diff --git a/chrome/content/zotero/elements/collapsibleSection.js b/chrome/content/zotero/elements/collapsibleSection.js
index 00cbc7b13b..539056063b 100644
--- a/chrome/content/zotero/elements/collapsibleSection.js
+++ b/chrome/content/zotero/elements/collapsibleSection.js
@@ -43,7 +43,8 @@
 		set open(newOpen) {
 			newOpen = !!newOpen;
 			let oldOpen = this.open;
-			if (oldOpen === newOpen || this.empty || !this.collapsible) return;
+			if (oldOpen === newOpen || this.empty) return;
+			if (!newOpen && !this.collapsible) return;
 			this.render();
 			
 			// Force open before getting scrollHeight, so we get the right value
@@ -118,9 +119,22 @@
 				this.setAttribute('no-collapse', val);
 			}
 		}
-		
+
+		get showContextMenu() {
+			return !this.getAttribute("no-context-menu");
+		}
+
+		set showContextMenu(val) {
+			if (val) {
+				this.removeAttribute('no-context-menu');
+			}
+			else {
+				this.setAttribute('no-context-menu', val);
+			}
+		}
+
 		static get observedAttributes() {
-			return ['open', 'empty', 'label', 'summary', 'extra-buttons'];
+			return ['open', 'empty', 'label', 'summary', 'extra-buttons', 'no-collapse'];
 		}
 		
 		attributeChangedCallback(name) {
@@ -348,7 +362,7 @@
 		}
 		
 		_saveOpenState() {
-			if (this._disableSavingOpenState) return;
+			if (this._disableSavingOpenState || this._skipSaveOpenState) return;
 			Zotero.Prefs.set(`panes.${this.dataset.pane}.open`, this.open);
 		}
 		
@@ -383,11 +397,11 @@
 		}
 
 		get _disableContextMenu() {
-			return !this._getSidenav() || !!this.closest('annotation-items-pane');
+			return !this._getSidenav() || !this.showContextMenu || !!this.closest('annotation-items-pane');
 		}
 
 		_handleClick = (event) => {
-			if (this._disableCollapsing) return;
+			if (this._disableCollapsing || !this.collapsible) return;
 			if (event.target.closest('.section-custom-button, menupopup')) return;
 			this.open = !this.open;
 		};
@@ -417,7 +431,7 @@
 			}
 			// Space/Enter toggle section open/closed.
 			// ArrowLeft/ArrowRight on actual header will close/open (depending on locale direction)
-			if (["ArrowLeft", "ArrowRight", " ", "Enter"].includes(event.key) && !this._disableCollapsing) {
+			if (["ArrowLeft", "ArrowRight", " ", "Enter"].includes(event.key) && !this._disableCollapsing && this.collapsible) {
 				stopEvent();
 				this.open = ([" ", "Enter"].includes(event.key)) ? !this.open : (event.key == Zotero.arrowNextKey);
 				event.target.focus();
@@ -480,7 +494,7 @@
 			this._title.textContent = this.label;
 			this._summary.textContent = this.summary;
 			let twisty = this._head.querySelector('.twisty');
-			twisty.hidden = this._disableCollapsing;
+			twisty.hidden = this._disableCollapsing || !this.collapsible;
 			document.l10n.setAttributes(twisty, `section-button-${this.open ? "collapse" : "expand"}`, { section: this._paneName || "" });
 		}
 	}
diff --git a/chrome/content/zotero/elements/editableText.js b/chrome/content/zotero/elements/editableText.js
index 22bf14ade1..e331b857bd 100644
--- a/chrome/content/zotero/elements/editableText.js
+++ b/chrome/content/zotero/elements/editableText.js
@@ -137,6 +137,14 @@
 			this.setAttribute('value', value || '');
 		}
 		
+		get values() {
+			return this._values ? this._values : [this.value];
+		}
+		
+		set values(values) {
+			this._values = values;
+		}
+		
 		get initialValue() {
 			return this._input?.dataset.initialValue ?? '';
 		}
@@ -180,6 +188,23 @@
 			return this._input;
 		}
 
+		get multipleValues() {
+			return this.hasAttribute('multiple-values');
+		}
+		
+		set multipleValues(multipleValues) {
+			this.toggleAttribute('multiple-values', !!multipleValues);
+		}
+		
+		// true if the value is unchanged since the last blur event. Relevant for batch editing.
+		get cancelled() {
+			return this.hasAttribute('cancelled');
+		}
+
+		set cancelled(cancelled) {
+			this.toggleAttribute('cancelled', !!cancelled);
+		}
+
 		_resetTextDirection() {
 			this._input?.removeAttribute('dir');
 		}
@@ -275,7 +300,15 @@
 				}
 			}
 			this._input.readOnly = this.readOnly;
-			this._input.placeholder = this.placeholder;
+			if (this.readOnly && this.multipleValues) {
+				this._input.tabIndex = -1;
+			}
+			else {
+				this._input.removeAttribute('tabindex');
+			}
+			if (!(this.multipleValues && this.focused)) {
+				this._input.placeholder = this.placeholder;
+			}
 
 			if (this._input.tagName == "textarea") {
 				// Reset to initial state
@@ -381,6 +414,9 @@
 				this._ignoredWindowInactiveBlur = false;
 				return;
 			}
+			
+			this.cancelled = false;
+			this._clearValue = false;
 
 			let valueBeforeFocus = this.value;
 			this.dispatchEvent(new CustomEvent('focus'));
@@ -400,7 +436,15 @@
 			}
 
 			if (!('initialValue' in this._input.dataset)) {
-				this._input.dataset.initialValue = this._input.value;
+				this._input.dataset.initialValue = this.value;
+			}
+			
+			if (this.multipleValues) {
+				this._input.placeholder = '';
+				this._input.value = '';
+				if (this._input.mController) {
+					this._input.mController.startSearch("");
+				}
 			}
 		};
 		
@@ -410,12 +454,22 @@
 				this._ignoredWindowInactiveBlur = true;
 				return;
 			}
+
+			if (this.multipleValues) {
+				if (this.cancelled || (this._input.value === '' && !this._clearValue)) {
+					this.value = '';
+					this.placeholder = Zotero.getString('item-pane-batch-editing-multiple-values-placeholder');
+					this.cancelled = true;
+				}
+			}
+			
 			this.dispatchEvent(new Event('blur'));
 			this._resetStateAfterBlur();
 		};
 		
 		_resetStateAfterBlur() {
 			this._ignoredWindowInactiveBlur = false;
+			this._clearValue = false;
 			this._focusMousedownEvent = null;
 			this.classList.remove('focused');
 			this._input.scrollLeft = 0;
@@ -436,9 +490,14 @@
 				}
 			}
 			else if (event.key === 'Escape') {
-				let initialValue = this._input.dataset.initialValue ?? '';
-				this.setAttribute('value', initialValue);
-				this._input.value = initialValue;
+				if (this.multipleValues) {
+					this.cancelled = true;
+				}
+				else {
+					let initialValue = this._input.dataset.initialValue ?? '';
+					this.setAttribute('value', initialValue);
+					this._input.value = initialValue;
+				}
 				this._input.blur();
 			}
 		};
@@ -460,6 +519,10 @@
 		};
 		
 		_handleMouseDown = (event) => {
+			if (this.readOnly && this.multipleValues) {
+				event.preventDefault();
+				return;
+			}
 			// Prevent a right-click from focusing the input when unfocused
 			if (event.button === 2 && document.activeElement !== this._input) {
 				event.preventDefault();
diff --git a/chrome/content/zotero/elements/itemBox.js b/chrome/content/zotero/elements/itemBox.js
index 7016085b19..02384a0a62 100644
--- a/chrome/content/zotero/elements/itemBox.js
+++ b/chrome/content/zotero/elements/itemBox.js
@@ -50,6 +50,8 @@
 			this.eventHandlers = [];
 			this.itemTypeMenu = null;
 			
+			this._extraItems = [];
+			this._unionFieldDescriptors = null;
 			this._mode = 'view';
 			this._visibleFields = [];
 			this._hiddenFields = [];
@@ -275,6 +277,19 @@
 				this.updateCustomRowProperty(rowElem);
 			}
 		}
+
+		get extraItems() {
+			return this._extraItems;
+		}
+
+		set extraItems(val) {
+			if (!Array.isArray(val)) {
+				return;
+			}
+			this._extraItems = val.filter(item => item instanceof Zotero.Item && item.isRegularItem());
+			this._unionFieldDescriptors = null;
+			this._resetRenderedFlags();
+		}
 		
 		// .ref is an alias for .item
 		get ref() {
@@ -438,8 +453,60 @@
 			}
 		}
 
+		/**
+		 * Compute the union of fields across all selected item types for cross-type
+		 * batch editing. Returns null if all items share the same type (caller should
+		 * fall back to the normal single-type field list).
+		 *
+		 * Each descriptor in the returned array has:
+		 *   canonicalName -- base field name if base-mapped, else the original field name
+		 *   label -- localized label per the labeling rules
+		 */
+		_computeUnionFieldList() {
+			let allItems = [this.item, ...this._extraItems];
+			let allTypeIDs = [...new Set(allItems.map(i => i.itemTypeID))];
+
+			// Same-type batch -- use normal single-type logic
+			if (allTypeIDs.length === 1) return null;
+
+			let fieldMap = new Map(); // canonicalName -> descriptor
+			let orderCounter = 0;
+
+			for (let typeID of allTypeIDs) {
+				let typeFieldIDs = Zotero.ItemFields.getItemTypeFields(typeID);
+				for (let fieldID of typeFieldIDs) {
+					let fieldName = Zotero.ItemFields.getName(fieldID);
+
+					// Resolve to base field name if a mapping exists
+					let baseID = Zotero.ItemFields.getBaseIDFromTypeAndField(typeID, fieldID);
+					let canonicalName = baseID
+						? Zotero.ItemFields.getName(baseID)
+						: fieldName;
+
+					if (fieldMap.has(canonicalName)) {
+						// Shared by multiple types -- use base field label
+						fieldMap.get(canonicalName).label
+							= Zotero.ItemFields.getLocalizedString(canonicalName);
+					}
+					else {
+						fieldMap.set(canonicalName, {
+							canonicalName,
+							firstOrder: orderCounter++,
+							// Use type-specific label until another type shares this field
+							label: Zotero.ItemFields.getLocalizedString(fieldName),
+						});
+					}
+				}
+			}
+
+			let result = [...fieldMap.values()];
+			result.sort((a, b) => a.firstOrder - b.firstOrder);
+			return result;
+		}
+
 		_renderInternal() {
 			this._saveFieldFocus();
+			this._unionFieldDescriptors = null;
 
 			delete this._linkMenu.dataset.link;
 
@@ -462,7 +529,9 @@
 			}
 
 			// Item type menu
-			this.addItemTypeMenu();
+			if (!this._extraItems?.length) {
+				this.addItemTypeMenu();
+			}
 			this.updateItemTypeMenuSelection();
 			var fieldNames = [];
 			
@@ -473,9 +542,29 @@
 				}
 			}
 			// Get field order from database
+			else if (this._extraItems.length) {
+				// Batch editing -- compute field list
+				let unionFields = this._computeUnionFieldList();
+				if (unionFields) {
+					// Cross-type batch: use union of fields from all item types
+					this._unionFieldDescriptors = new Map();
+					for (let desc of unionFields) {
+						fieldNames.push(desc.canonicalName);
+						this._unionFieldDescriptors.set(desc.canonicalName, desc);
+					}
+				}
+				else {
+					// Same-type batch: use the shared item type's fields
+					let fields = Zotero.ItemFields.getItemTypeFields(this.item.getField("itemTypeID"));
+					for (let i = 0; i < fields.length; i++) {
+						fieldNames.push(Zotero.ItemFields.getName(fields[i]));
+					}
+				}
+				fieldNames.push("dateAdded", "dateModified");
+			}
 			else {
 				var fields = Zotero.ItemFields.getItemTypeFields(this.item.getField("itemTypeID"));
-				
+
 				for (let i = 0; i < fields.length; i++) {
 					fieldNames.push(Zotero.ItemFields.getName(fields[i]));
 				}
@@ -496,10 +585,14 @@
 					continue;
 				}
 				let val = '';
+				let extraFieldValues = [];
 				
 				if (fieldName) {
 					var fieldID = Zotero.ItemFields.getID(fieldName);
-					if (fieldID && !Zotero.ItemFields.isValidForType(fieldID, this.item.itemTypeID)) {
+					// In cross-type batch mode, union fields are pre-validated
+					if (!this._unionFieldDescriptors
+							&& fieldID
+							&& !Zotero.ItemFields.isValidForType(fieldID, this.item.itemTypeID)) {
 						fieldName = null;
 					}
 				}
@@ -519,11 +612,20 @@
 					else if (fieldName == 'feed') {
 						val = Zotero.Feeds.get(this.item.libraryID)?.name;
 					}
+					else if (this._unionFieldDescriptors) {
+						val = this.item.getField(fieldName, false, true);
+						extraFieldValues = this._extraItems.map(item => item.getField(fieldName, false, true));
+					}
 					else {
 						val = this.item.getField(fieldName);
+
+						if (this._extraItems.length) {
+							extraFieldValues = this._extraItems.map(item => item.getField(fieldName));
+						}
 					}
 					
-					if (!val && this.hideEmptyFields
+					if (!val && !extraFieldValues.some(v => v)
+							&& this.hideEmptyFields
 							&& this._visibleFields.indexOf(fieldName) == -1
 							&& (this.mode != 'fieldmerge' || typeof this._fieldAlternatives[fieldName] == 'undefined')) {
 						continue;
@@ -536,7 +638,10 @@
 							&& Zotero.ItemFields.isDate(fieldName)
 							// TEMP - NSF
 							&& fieldName != 'dateSent') {
-						this.addDateRow(fieldName, this.item.getField(fieldName, true));
+						let dateVal = this._unionFieldDescriptors
+							? this.item.getField(fieldName, true, true)
+							: this.item.getField(fieldName, true);
+						this.addDateRow(fieldName, dateVal, extraFieldValues);
 						continue;
 					}
 				}
@@ -546,12 +651,14 @@
 				rowLabel.setAttribute('fieldname', fieldName);
 				
 				let valueElement = this.createFieldValueElement(
-					val, fieldName
+					val, fieldName, extraFieldValues
 				);
 				
 				if (fieldName) {
+					let labelText = this._unionFieldDescriptors?.get(fieldName)?.label
+						?? Zotero.ItemFields.getLocalizedString(fieldName);
 					let label = this.createLabelElement({
-						text: Zotero.ItemFields.getLocalizedString(fieldName),
+						text: labelText,
 						id: `itembox-field-${fieldName}-label`,
 					});
 					rowLabel.appendChild(label);
@@ -560,8 +667,12 @@
 				let openLinkButton;
 				let link = val;
 				let addLinkContextMenu = false;
+				// Don't show View Online button in batch edit mode
+				if (this._extraItems.length) {
+					// No open-link button in batch edit mode
+				}
 				// TEMP - NSF (homepage)
-				if ((fieldName == 'url' || fieldName == 'homepage')
+				else if ((fieldName == 'url' || fieldName == 'homepage')
 						// Only make plausible HTTP URLs clickable
 						&& Zotero.Utilities.isHTTPURL(val, true)) {
 					openLinkButton = this.createOpenLinkIcon(val, fieldName);
@@ -636,8 +747,8 @@
 					onContextMenu = this.createContextMenuHandler(fieldName, () => {
 						let menupopup = ZoteroPane.buildFieldTransformMenu({
 							target: valueElement,
-							onTransform: (newValue) => {
-								this._setFieldTransformedValue(valueElement, newValue);
+							onTransform: (newValues) => {
+								this._setFieldTransformedValue(valueElement, newValues);
 							}
 						});
 						this.querySelector('#info-box > popupset').append(menupopup);
@@ -711,6 +822,11 @@
 						labelKey = 'items-column-modified-by';
 					}
 					if (userID) {
+						let hasMultipleUsers = fieldName === 'dateAdded'
+							? this._extraItems.some(item => item.createdByUserID !== userID)
+							: this._extraItems.some(
+								item => (item.lastModifiedByUserID || item.createdByUserID) !== userID
+							);
 						let userLabel = document.createElement("div");
 						userLabel.className = "meta-label";
 						userLabel.setAttribute("fieldname", userFieldName);
@@ -720,9 +836,18 @@
 						}));
 						let userData = document.createElement("div");
 						userData.className = "meta-data";
-						userData.appendChild(this.createValueElement({
-							text: Zotero.Users.getName(userID),
-						}));
+						let valueElem = this.createValueElement({
+							text: hasMultipleUsers ? '' : Zotero.Users.getName(userID),
+						});
+						if (this._extraItems.length) {
+							valueElem.multipleValues = true;
+							if (hasMultipleUsers) {
+								valueElem.placeholder = Zotero.getString(
+									'item-pane-batch-editing-multiple-values-placeholder'
+								);
+							}
+						}
+						userData.appendChild(valueElem);
 						this.addDynamicRow(userLabel, userData);
 					}
 				}
@@ -731,103 +856,108 @@
 			//
 			// Creators
 			//
-			
-			// Creator type menu
-			if (this.editable) {
-				while (this._creatorTypeMenu.hasChildNodes()) {
-					this._creatorTypeMenu.removeChild(this._creatorTypeMenu.firstChild);
-				}
-				
-				var creatorTypes = Zotero.CreatorTypes.getTypesForItemType(this.item.itemTypeID);
-	
-				var localized = {};
-				for (let i = 0; i < creatorTypes.length; i++) {
-					localized[creatorTypes[i].name]
-						= Zotero.CreatorTypes.getLocalizedString(creatorTypes[i].name);
-				}
-				
-				for (let i in localized) {
-					var menuitem = document.createXULElement("menuitem");
-					menuitem.setAttribute("label", localized[i]);
-					menuitem.setAttribute("typeid", Zotero.CreatorTypes.getID(i));
-					this._creatorTypeMenu.appendChild(menuitem);
-				}
-				this._creatorTypeMenu.addEventListener('popuphidden', () => {
-					// If the popup was opened with a mouse click, blur the field to hide icons
-					if (this._creatorTypeMenu.getAttribute("blur-on-hidden")) {
-						document.activeElement.blur();
-						this._creatorTypeMenu.removeAttribute("blur-on-hidden");
+			// If batch-editing, skip creators (for now)
+			if (!this._extraItems?.length) {
+				// Creator type menu
+				if (this.editable) {
+					while (this._creatorTypeMenu.hasChildNodes()) {
+						this._creatorTypeMenu.removeChild(this._creatorTypeMenu.firstChild);
 					}
-				});
-			}
-			
-			// Creator rows
-			
-			// Place, in order of preference, after title, after type,
-			// or at beginning
-			var field = this.getTitleField();
-			if (!field) {
-				field = this._infoTable.querySelector('[fieldName="itemType"]');
-			}
-			if (field) {
-				this._firstRowBeforeCreators = field.closest(".meta-row").nextSibling;
-			}
-			else {
-				this._firstRowBeforeCreators = this._infoTable.firstChild;
-			}
-			
-			this._creatorCount = 0;
-			var num = this.item.numCreators();
-			if (num > 0) {
-				// Limit number of creators display
-				var max = Math.min(num, this._initialVisibleCreators);
-				// If only 1 or 2 more, just display
-				if (num < max + 3 || this._displayAllCreators) {
-					max = num;
-				}
-				for (let i = 0; i < max; i++) {
-					let data = this.item.getCreator(i);
-					this.addCreatorRow(data, data.creatorTypeID, false);
-				}
-				if (this._draggedCreator) {
-					this._draggedCreator = false;
-					// Block hover effects on creators, enable them back on first mouse movement.
-					// See comment in creatorDragPlaceholder() for explanation
-					for (let label of document.querySelectorAll(".meta-label[fieldname^='creator-']")) {
-						label.closest(".meta-row").classList.add("noHover");
+					
+					var creatorTypes = Zotero.CreatorTypes.getTypesForItemType(this.item.itemTypeID);
+		
+					var localized = {};
+					for (let i = 0; i < creatorTypes.length; i++) {
+						localized[creatorTypes[i].name]
+							= Zotero.CreatorTypes.getLocalizedString(creatorTypes[i].name);
 					}
-					let removeHoverBlock = () => {
-						let noHoverRows = document.querySelectorAll('.noHover');
-						noHoverRows.forEach(el => el.classList.remove('noHover'));
-						document.removeEventListener('mousemove', removeHoverBlock);
-					};
-					document.addEventListener('mousemove', removeHoverBlock);
+					
+					for (let i in localized) {
+						var menuitem = document.createXULElement("menuitem");
+						menuitem.setAttribute("label", localized[i]);
+						menuitem.setAttribute("typeid", Zotero.CreatorTypes.getID(i));
+						this._creatorTypeMenu.appendChild(menuitem);
+					}
+					this._creatorTypeMenu.addEventListener('popuphidden', () => {
+						// If the popup was opened with a mouse click, blur the field to hide icons
+						if (this._creatorTypeMenu.getAttribute("blur-on-hidden")) {
+							document.activeElement.blur();
+							this._creatorTypeMenu.removeAttribute("blur-on-hidden");
+						}
+					});
 				}
 				
-				// Additional creators not displayed
-				if (num > max) {
-					this.addMoreCreatorsRow(num - max);
+				// Creator rows
+				
+				// Place, in order of preference, after title, after type,
+				// or at beginning
+				var field = this.getTitleField();
+				if (!field) {
+					field = this._infoTable.querySelector('[fieldName="itemType"]');
+				}
+				if (field) {
+					this._firstRowBeforeCreators = field.closest(".meta-row").nextSibling;
 				}
 				else {
-					// If we didn't start with creators truncated,
-					// don't truncate for as long as we're viewing
-					// this item, so that added creators aren't
-					// immediately hidden
-					this._displayAllCreators = true;
+					this._firstRowBeforeCreators = this._infoTable.firstChild;
+				}
+
+				this._creatorCount = 0;
+				var num = this.item.numCreators();
+				if (num > 0) {
+					// Limit number of creators display
+					var max = Math.min(num, this._initialVisibleCreators);
+					// If only 1 or 2 more, just display
+					if (num < max + 3 || this._displayAllCreators) {
+						max = num;
+					}
+					for (let i = 0; i < max; i++) {
+						let data = this.item.getCreator(i);
+						this.addCreatorRow(data, data.creatorTypeID, false);
+					}
+					if (this._draggedCreator) {
+						this._draggedCreator = false;
+						// Block hover effects on creators, enable them back on first mouse movement.
+						// See comment in creatorDragPlaceholder() for explanation
+						for (let label of document.querySelectorAll(".meta-label[fieldname^='creator-']")) {
+							label.closest(".meta-row")
+								.classList
+								.add("noHover");
+						}
+						let removeHoverBlock = () => {
+							let noHoverRows = document.querySelectorAll('.noHover');
+							noHoverRows.forEach(el => el.classList.remove('noHover'));
+							document.removeEventListener('mousemove', removeHoverBlock);
+						};
+						document.addEventListener('mousemove', removeHoverBlock);
+					}
+
+					// Additional creators not displayed
+					if (num > max) {
+						this.addMoreCreatorsRow(num - max);
+					}
+					else {
+						// If we didn't start with creators truncated,
+						// don't truncate for as long as we're viewing
+						// this item, so that added creators aren't
+						// immediately hidden
+						this._displayAllCreators = true;
+					}
+				}
+				else if (this.editable && Zotero.CreatorTypes.itemTypeHasCreators(this.item.itemTypeID)) {
+					// Add default row
+					this.addCreatorRow(false, false, false);
+				}
+
+
+				if (this._showCreatorTypeGuidance) {
+					let creatorTypeLabels = this.querySelectorAll(".creator-type-label");
+					this._id("zotero-author-guidance")
+						.show({
+							forEl: creatorTypeLabels[creatorTypeLabels.length - 1]
+						});
+					this._showCreatorTypeGuidance = false;
 				}
-			}
-			else if (this.editable && Zotero.CreatorTypes.itemTypeHasCreators(this.item.itemTypeID)) {
-				// Add default row
-				this.addCreatorRow(false, false, false);
-			}
-			
-			
-			if (this._showCreatorTypeGuidance) {
-				let creatorTypeLabels = this.querySelectorAll(".creator-type-label");
-				this._id("zotero-author-guidance").show({
-					forEl: creatorTypeLabels[creatorTypeLabels.length - 1]
-				});
-				this._showCreatorTypeGuidance = false;
 			}
 
 			this._ensureButtonsFocusable();
@@ -1433,12 +1563,14 @@
 			this.addDynamicRow(rowLabel, rowData);
 		}
 		
-		addDateRow(field, value) {
+		addDateRow(field, value, extraFieldValues) {
 			var rowLabel = document.createElement("div");
 			rowLabel.className = "meta-label";
 			rowLabel.setAttribute("fieldname", field);
+			let labelText = this._unionFieldDescriptors?.get(field)?.label
+				?? Zotero.ItemFields.getLocalizedString(field);
 			let label = this.createLabelElement({
-				text: Zotero.ItemFields.getLocalizedString(field),
+				text: labelText,
 				id: `itembox-field-${field}-label`
 			});
 			rowLabel.appendChild(label);
@@ -1448,18 +1580,21 @@
 			
 			var elem = this.createFieldValueElement(
 				Zotero.Date.multipartToStr(value),
-				field
+				field,
+				extraFieldValues
 			);
 
 			elem.setAttribute('aria-labelledby', label.id);
-			// y-m-d status indicator
-			var ymd = document.createElement('span');
-			ymd.id = 'zotero-date-field-status';
-			ymd.textContent = Zotero.Date.strToDate(Zotero.Date.multipartToStr(value))
-					.order.split('').join(' ');
-			ymd.className = "show-on-hover";
 			rowData.appendChild(elem);
-			rowData.appendChild(ymd);
+			// Don't show y-m-d status indicator in batch edit mode
+			if (!this._extraItems.length) {
+				var ymd = document.createElement('span');
+				ymd.id = 'zotero-date-field-status';
+				ymd.textContent = Zotero.Date.strToDate(Zotero.Date.multipartToStr(value))
+						.order.split('').join(' ');
+				ymd.className = "show-on-hover";
+				rowData.appendChild(ymd);
+			}
 			
 			rowData.oncontextmenu = this.createContextMenuHandler(field);
 			
@@ -1750,7 +1885,7 @@
 			return valueElement;
 		}
 
-		createFieldValueElement(valueText, fieldName) {
+		createFieldValueElement(valueText, fieldName, extraFieldValues = []) {
 			valueText += '';
 
 			if (fieldName) {
@@ -1786,7 +1921,7 @@
 			}
 			
 			let tooltipText;
-			if (fieldID) {
+			if (fieldID && !this._extraItems.length) {
 				// Display the SQL date as a tooltip for date fields
 				// TEMP - filingDate
 				if (Zotero.ItemFields.isFieldOfBase(fieldID, 'date') || fieldName == 'filingDate') {
@@ -1823,6 +1958,53 @@
 				// autocomplete for creator names is added in addCreatorRow
 				this.addAutocompleteToElement(valueElement);
 			}
+			
+			valueElement.values = [valueText, ...extraFieldValues];
+			const hasMultipleValues = extraFieldValues.length && extraFieldValues.some(v => v !== valueText);
+			if (hasMultipleValues) {
+				let allValues = [valueText, ...extraFieldValues];
+				let optionCounts = {};
+				for (let v of allValues) {
+					if (v.length > 0) {
+						optionCounts[v] = (optionCounts[v] || 0) + 1;
+					}
+				}
+				let options = Object.keys(optionCounts);
+				options.sort((a, b) => a.localeCompare(b, undefined, { sensitivity: 'base', numeric: true }));
+				let optionLabels = options.map(o => `[${optionCounts[o]}] ${o}`);
+				valueElement.multipleValues = true;
+				valueElement.value = '';
+				valueElement.placeholder = Zotero.getString('item-pane-batch-editing-multiple-values-placeholder');
+				if (this._fieldIsClickable(fieldName)) {
+					valueElement.initialValue = valueText;
+					valueElement.autocomplete = {
+						minResultsForPopup: 1,
+						noRollupOnEmptySearch: true,
+						completeSelectedIndex: true,
+						ignoreBlurWhileSearching: false,
+						search: 'zotero-options',
+						searchParam: JSON.stringify({
+							search: 'zotero-options',
+							options: optionLabels,
+							optionValues: options,
+							includeNoValue: true
+						}),
+						popup: 'PopupAutoComplete',
+					};
+					valueElement.onTextEntered = () => {
+						let input = valueElement.ref;
+						let controller = input?.controller;
+						if (!controller?.matchCount) return;
+						let selectedIndex = input.popup?.selectedIndex ?? -1;
+						if (selectedIndex >= 0
+								&& controller.getStyleAt(selectedIndex) === 'options-ac-no-value') {
+							valueElement._clearValue = true;
+							valueElement.blur();
+						}
+					};
+				}
+			}
+
 			return valueElement;
 		}
 		
@@ -1915,7 +2097,9 @@
 				}
 			}
 			else {
-				value = this.item.getField(fieldName);
+				value = this._unionFieldDescriptors
+					? this.item.getField(fieldName, false, true)
+					: this.item.getField(fieldName);
 				// Access date needs to be converted from UTC
 				if (value != '') {
 					let localDate;
@@ -2155,6 +2339,10 @@
 			if (this.ignoreBlur || !textbox) {
 				return;
 			}
+			
+			if (textbox.cancelled) {
+				return;
+			}
 
 			var fieldName = textbox.getAttribute('fieldname');
 
@@ -2292,7 +2480,7 @@
 			}
 			
 			if (this.saveOnEdit) {
-				await this.item.saveTx();
+				await this._saveItems();
 			}
 		}
 		
@@ -2308,24 +2496,66 @@
 					|| this._clickableFields.indexOf(fieldName) != -1);
 		}
 		
-		_modifyField(field, value) {
-			this.item.setField(field, value);
+		/**
+		 * Check whether a field can be set on an item, considering base field mappings.
+		 */
+		_canSetFieldOnItem(field, item) {
+			let fieldID = Zotero.ItemFields.getID(field);
+			if (!fieldID) return false;
+			if (Zotero.ItemFields.isValidForType(fieldID, item.itemTypeID)) return true;
+			return !!Zotero.ItemFields.getFieldIDFromTypeAndBase(item.itemTypeID, fieldID);
+		}
+
+		_modifyField(field, value, item = null) {
+			let items = item ? [item] : [this.item, ...this._extraItems];
+			for (let i of items) {
+				if (this._unionFieldDescriptors && !this._canSetFieldOnItem(field, i)) {
+					continue;
+				}
+				i.setField(field, value);
+			}
 		}
 		
-		async _setFieldTransformedValue(label, newValue) {
-			label.value = newValue;
-			var fieldName = label.getAttribute('fieldname');
-			this._modifyField(fieldName, newValue);
+		async _saveItems() {
+			// Cache item and extra items to avoid a race condition where, after `hideEditor`,
+			// while we yield for `await Zotero.DB.executeTransaction`, itemBox is rendered for
+			// the new item and this.item is no longer relevant
+			let item = this.item;
+			let extraItems = this._extraItems;
 			
-			if (Zotero.ItemFields.isFieldOfBase(fieldName, 'title')) {
-				let shortTitleVal = this.item.getField('shortTitle');
-				if (newValue.toLowerCase().startsWith(shortTitleVal.toLowerCase())) {
-					this._modifyField('shortTitle', newValue.substring(0, shortTitleVal.length));
+			await Zotero.DB.executeTransaction(async () => {
+				await item.save();
+				for (let extraItem of extraItems) {
+					await extraItem.save();
 				}
+			});
+			if (extraItems.length) {
+				this._forceRenderAll();
 			}
+		}
+		
+		async _setFieldTransformedValue(label, newValues) {
+			let fieldName = label.getAttribute('fieldname');
+			// In batch mode, don't update the label -- it shows a "Multiple" placeholder
+			// that should remain unchanged.
+			if (!this._extraItems.length) {
+				label.value = newValues[0];
+			}
+			let items = [this.item, ...this._extraItems];
+			items.forEach((item, index) => {
+				let newValue = newValues[index];
+				this._modifyField(fieldName, newValue, item);
+				
+				if (Zotero.ItemFields.isFieldOfBase(fieldName, 'title')) {
+					let shortTitleVal = item.getField('shortTitle');
+					if (newValue.toLowerCase().startsWith(shortTitleVal.toLowerCase())) {
+						this._modifyField('shortTitle', newValue.substring(0, shortTitleVal.length), item);
+					}
+				}
+			});
 
 			if (this.saveOnEdit) {
-				await this.item.saveTx();
+				await this._saveItems();
 			}
 		}
 		
@@ -2651,6 +2881,9 @@
 		}
 
 		getTitleField() {
+			if (this._unionFieldDescriptors) {
+				return this._infoTable.querySelector('editable-text[fieldname="title"]');
+			}
 			var titleFieldID = Zotero.ItemFields.getFieldIDFromTypeAndBase(this.item.itemTypeID, 'title');
 			return this._infoTable.querySelector(`editable-text[fieldname="${Zotero.ItemFields.getName(titleFieldID)}"]`);
 		}
diff --git a/chrome/content/zotero/elements/itemDetails.js b/chrome/content/zotero/elements/itemDetails.js
index 2c6ea9c1e5..651a3954cf 100644
--- a/chrome/content/zotero/elements/itemDetails.js
+++ b/chrome/content/zotero/elements/itemDetails.js
@@ -88,6 +88,18 @@
 			this._item = item;
 		}
 
+		get extraItems() {
+			return this._extraItems ?? [];
+		}
+
+		set extraItems(val) {
+			if (!Array.isArray(val)) {
+				return;
+			}
+
+			this._extraItems = val.filter(item => item instanceof Zotero.Item && item.isRegularItem());
+		}
+
 		/*
 		 * For contextPane update
 		 */
@@ -293,7 +305,12 @@
 				box.tabID = this.tabID;
 				box.tabType = this.tabType;
 				box.item = item;
+				box.extraItems = this.extraItems;
 				box.collectionTreeRow = this.collectionTreeRow;
+				if (this.extraItems.length > 0) {
+					// mark everything, except the header and the info pane, as hidden
+					box.hidden = box.dataset.pane !== 'info' && box !== this._header;
+				}
 				// Discard hidden panes
 				if (box.hidden && box.discard) {
 					box.discard();
diff --git a/chrome/content/zotero/elements/itemPane.js b/chrome/content/zotero/elements/itemPane.js
index 21aff91a44..8f26678546 100644
--- a/chrome/content/zotero/elements/itemPane.js
+++ b/chrome/content/zotero/elements/itemPane.js
@@ -40,8 +40,11 @@
 					previousfocus="zotero-items-tree" />
 				
 				<duplicates-merge-pane id="zotero-duplicates-merge-pane" />
-
 				<annotation-items-pane id="zotero-annotations-pane" />
+				<groupbox id="batch-edit-prompt" pack="center" align="center" data-l10n-id="item-pane-batch-editing-prompt">
+					<description id="batch-edit-prompt-message" />
+					<button id="batch-edit-prompt-enable" data-l10n-id="item-pane-batch-editing-enable" />
+				</groupbox>
 			</deck>
 			<item-pane-sidenav id="zotero-view-item-sidenav" no-context-notes="true" class="zotero-view-item-sidenav"/>
 		`);
@@ -52,6 +55,8 @@
 			this._duplicatesPane = this.querySelector("#zotero-duplicates-merge-pane");
 			this._messagePane = this.querySelector("#zotero-item-message");
 			this._annotationsPane = this.querySelector("#zotero-annotations-pane");
+			this._batchEditEnableBtn = this.querySelector("#batch-edit-prompt button");
+			this._batchEditPromptMessage = this.querySelector("#batch-edit-prompt-message");
 			this._sidenav = this.querySelector("#zotero-view-item-sidenav");
 			this._deck = this.querySelector("#zotero-item-pane-content");
 
@@ -59,6 +64,14 @@
 
 			this._notifierID = Zotero.Notifier.registerObserver(this, ['item']);
 
+			this._batchEditEnableBtn.addEventListener("command", () => {
+				this._isBatchEditEnabled = true;
+				this._setBatchEditCollapsible(true);
+				this.render();
+				this.updateItemPaneButtons();
+			});
+			
+			this._isBatchEditEnabled = false;
 			this._translationTarget = null;
 		}
 
@@ -100,12 +113,12 @@
 		}
 
 		get mode() {
-			return ["message", "item", "note", "duplicates"][this._deck.selectedIndex];
+			return ["message", "item", "note", "duplicates", "annotations", "batch-edit-prompt"][this._deck.selectedIndex];
 		}
 
 		/**
 		 * Set mode of item pane
-		 * @param {"message" | "item" | "note" | "duplicates"} type view type
+		 * @param {"message" | "item" | "note" | "duplicates" | "annotations" | "batch-edit-prompt"} type view type
 		 */
 		set mode(type) {
 			this.setAttribute("view-type", type);
@@ -126,10 +139,26 @@
 			if (this.data.length > 0 && this.data.every(item => item.isAnnotation())) {
 				return renderStatus = this.renderAnnotations(this.data);
 			}
+			
+			// reset the batch editing flag
+			let IDs = this.data.map(item => item.id);
+			if (!(IDs.length === this._prevIDs?.length && IDs.every((id, i) => id === this._prevIDs?.[i]))) {
+				if (this._isBatchEditEnabled) {
+					this._setBatchEditCollapsible(false);
+				}
+				this._isBatchEditEnabled = false;
+				this._prevIDs = IDs;
+			}
+			
+			// Multiple items selected (not duplicates)
+			if (!this.collectionTreeRow.isDuplicates() && this.data.length > 1 && this.data.every(item => item.isRegularItem() && !item.isFeedItem)) {
+				// Hide the batch editing UI until the user opts-in
+				renderStatus = this._isBatchEditEnabled ? this.renderItemPane(this.data) : this.renderBatchEditorPrompt();
+			}
 			// Single item selected
-			if (this.data.length == 1) {
+			else if (this.data.length === 1) {
 				let item = this.data[0];
-				
+
 				// If a collection or search is selected, it must be in the trash.
 				if (item instanceof Zotero.Collection || item instanceof Zotero.Search) {
 					renderStatus = this.renderMessage();
@@ -141,7 +170,7 @@
 					renderStatus = this.renderItemPane(item);
 				}
 			}
-			// Zero or multiple items selected
+			// No items selected or multiple, but includes some irregular items
 			else {
 				renderStatus = this.renderMessage();
 			}
@@ -175,9 +204,12 @@
 			return true;
 		}
 
-		async renderItemPane(item) {
+		async renderItemPane(items) {
 			let previousMode = this.mode;
 			this.mode = "item";
+			if (!Array.isArray(items)) {
+				items = [items];
+			}
 
 			// Fix https://forums.zotero.org/discussion/115450/zotero-7-beta-wrong-vertical-position-in-the-item-pane-after-switching-from-a-note
 			if (previousMode === "note") {
@@ -186,11 +218,12 @@
 					requestIdleCallback(resolve, { timeout: 50 });
 				});
 			}
-			
+
 			this._itemDetails.editable = this.editable;
 			this._itemDetails.tabID = "zotero-pane";
 			this._itemDetails.tabType = "library";
-			this._itemDetails.item = item;
+			this._itemDetails.item = items[0];
+			this._itemDetails.extraItems = items.slice(1);
 			this._itemDetails.collectionTreeRow = this.collectionTreeRow;
 
 			this._itemDetails.render();
@@ -198,8 +231,8 @@
 			if (this.getAttribute("collapsed") == "true") {
 				return true;
 			}
-			
-			if (item.isFeedItem) {
+
+			if (items[0].isFeedItem) {
 				let lastTranslationTarget = Zotero.Prefs.get('feeds.lastTranslationTarget');
 				if (lastTranslationTarget) {
 					let id = parseInt(lastTranslationTarget.substr(1));
@@ -218,7 +251,7 @@
 				// if (!item.isTranslated) {
 				// 	item.translate();
 				// }
-				ZoteroPane.startItemReadTimeout(item.id);
+				ZoteroPane.startItemReadTimeout(items[0].id);
 			}
 			return true;
 		}
@@ -298,6 +331,16 @@
 			return true;
 		}
 
+		renderBatchEditorPrompt() {
+			this.mode = 'batch-edit-prompt';
+			document.l10n.setAttributes(
+				this._batchEditPromptMessage,
+				'item-pane-message-items-selected',
+				{ count: this.data.length }
+			);
+			return true;
+		}
+
 		setItemPaneMessage(msg) {
 			this.mode = "message";
 			this._messagePane.render(msg);
@@ -348,6 +391,11 @@
 				return;
 			}
 
+			if (this._isBatchEditEnabled && this.data.length > 1) {
+				container.renderCustomHead(this.renderBatchEditHead.bind(this));
+				return;
+			}
+			
 			container.renderCustomHead();
 		}
 
@@ -426,6 +474,17 @@
 			append(button);
 		}
 
+		renderBatchEditHead(data) {
+			let { doc, append } = data;
+			let description = doc.createXULElement("description");
+			document.l10n.setAttributes(
+				description,
+				'item-pane-batch-editing-header',
+				{ count: this.data.length }
+			);
+			append(description);
+		}
+
 		updateReadLabel() {
 			var items = this.data;
 			var isUnread = false;
@@ -535,6 +594,25 @@
 			this.setTranslateButton();
 		}
 
+		_setBatchEditCollapsible(enabled) {
+			let section = this._itemDetails.querySelector('collapsible-section[data-pane="info"]');
+			if (!section) return;
+			if (enabled) {
+				// Force open without saving to prefs, so the previous state is preserved
+				section._skipSaveOpenState = true;
+				section.open = true;
+				section._skipSaveOpenState = false;
+				section.collapsible = false;
+				section.showContextMenu = false;
+			}
+			else {
+				section.collapsible = true;
+				section.showContextMenu = true;
+				// Restore the pref-saved open state
+				section._restoreOpenState();
+			}
+		}
+
 		getCurrentPane(mode = undefined) {
 			if (!mode) {
 				// Guess a mode from the current data
@@ -543,7 +621,7 @@
 					mode = "annotations";
 				}
 				// No/multiple objects are selected OR selected object is a trashed collection/search
-				else if (!this.data.length || this.data.length > 1
+				else if (!this.data.length || (this.data.length > 1 && !this._isBatchEditEnabled)
 					|| this.data[0] instanceof Zotero.Collection || this.data[0] instanceof Zotero.Search) {
 					mode = "message";
 				}
@@ -642,6 +720,10 @@
 					this._deck.selectedIndex = 4;
 					break;
 				}
+				case "batch-edit-prompt": {
+					this._deck.selectedIndex = 5;
+					break;
+				}
 			}
 			let isViewingItem = type == "item";
 			if (previousViewType != "item" && isViewingItem) {
diff --git a/chrome/content/zotero/elements/itemPaneHeader.js b/chrome/content/zotero/elements/itemPaneHeader.js
index 41853cf001..bf206f6753 100644
--- a/chrome/content/zotero/elements/itemPaneHeader.js
+++ b/chrome/content/zotero/elements/itemPaneHeader.js
@@ -65,6 +65,10 @@
 
 		_editable = true;
 		
+		get _renderDependencies() {
+			return [this._tabID, this._item?.id, this.extraItems?.length ?? 0];
+		}
+
 		get item() {
 			return this._item;
 		}
@@ -145,8 +149,8 @@
 				event.preventDefault();
 				let menupopup = ZoteroPane.buildFieldTransformMenu({
 					target: this.titleField,
-					onTransform: (newValue) => {
-						this._setTransformedValue(newValue);
+					onTransform: (newValues) => {
+						this._setTransformedValue(newValues[0]);
 					},
 				});
 				
@@ -226,6 +230,12 @@
 			if (this._item.isAttachment()) {
 				headerMode = 'title';
 			}
+			
+			if (this.extraItems?.length) {
+				headerMode = 'none';
+			}
+
+			this.classList.toggle('batch-edit', !!this.extraItems?.length);
 
 			this.title.hidden = true;
 			this.creatorYear.hidden = true;
diff --git a/chrome/content/zotero/modules/optionsAutoComplete.mjs b/chrome/content/zotero/modules/optionsAutoComplete.mjs
new file mode 100644
index 0000000000..3db803bb26
--- /dev/null
+++ b/chrome/content/zotero/modules/optionsAutoComplete.mjs
@@ -0,0 +1,82 @@
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+const OPTIONS_AC_CLASS_ID = Components.ID('{882f1f42-c1ff-458c-9157-06a4a55d32e8}');
+const OPTIONS_AC_NAME = "zotero-options";
+const OPTIONS_AC_CONTRACT_ID = `@mozilla.org/autocomplete/search;1?name=${OPTIONS_AC_NAME}`;
+
+function makeResult(searchString, matches, { noValueLabel, values } = {}) {
+	const r = Cc["@mozilla.org/autocomplete/simple-result;1"]
+		.createInstance(Ci.nsIAutoCompleteSimpleResult);
+
+	r.setSearchString(searchString);
+
+	if (matches.length === 0 && !noValueLabel) {
+		r.setSearchResult(Ci.nsIAutoCompleteResult.RESULT_NOMATCH);
+		r.setDefaultIndex(-1);
+		return r;
+	}
+
+	r.setSearchResult(Ci.nsIAutoCompleteResult.RESULT_SUCCESS);
+	r.setDefaultIndex(0);
+
+	for (let i = 0; i < matches.length; i++) {
+		let label = matches[i];
+		let value = values?.[i] ?? label;
+		r.appendMatch(label, "", null, "options-ac-value", value, label);
+	}
+	if (noValueLabel) {
+		r.appendMatch("", noValueLabel, null, "options-ac-no-value", "", noValueLabel);
+	}
+	return r;
+}
+
+export class OptionsAutoComplete {
+	static init() {
+		const registrar = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+		if (registrar.isCIDRegistered(OPTIONS_AC_CLASS_ID)) {
+			return;
+		}
+		registrar.registerFactory(
+			OPTIONS_AC_CLASS_ID, "", OPTIONS_AC_CONTRACT_ID, new OptionsAutoComplete()
+		);
+	}
+
+	// nsIAutoCompleteSearch
+	startSearch(searchString, searchParams, previousResult, listener) {
+		searchParams = JSON.parse(searchParams);
+		if (!searchParams) {
+			throw new Error("Invalid JSON passed to autocomplete");
+		}
+
+		let allOptions = searchParams?.options ?? [];
+		let allValues = searchParams?.optionValues ?? allOptions;
+		let search = (searchString || "").toLowerCase();
+		let filtered = allOptions
+			.map((label, i) => ({ label, value: allValues[i] ?? label }))
+			.filter(({ value }) => value.toLowerCase().startsWith(search))
+			.slice(0, 10);
+		let matches = filtered.map(({ label }) => label);
+		let values = filtered.map(({ value }) => value);
+		let noValueLabel = searchParams?.includeNoValue && !searchString
+			? Zotero.getString('item-pane-batch-editing-no-value')
+			: null;
+		const result = makeResult(searchString, matches, { noValueLabel, values });
+		listener.onSearchResult(this, result);
+	}
+
+	// nsIAutoCompleteSearch
+	stopSearch() {
+	}
+
+	// nsIFactory
+	createInstance(iid) {
+		return this.QueryInterface(iid);
+	}
+}
+
+OptionsAutoComplete.prototype.classID = OPTIONS_AC_CLASS_ID;
+OptionsAutoComplete.prototype.QueryInterface = ChromeUtils.generateQI([
+	"nsIFactory",
+	"nsIAutoCompleteSearch",
+]);
diff --git a/chrome/content/zotero/xpcom/zotero.js b/chrome/content/zotero/xpcom/zotero.js
index e6c17ba7b8..26b4d84a86 100644
--- a/chrome/content/zotero/xpcom/zotero.js
+++ b/chrome/content/zotero/xpcom/zotero.js
@@ -671,8 +671,15 @@ const { CommandLineOptions } = ChromeUtils.importESModule("chrome://zotero/conte
 			const { ZoteroAutoComplete } = ChromeUtils.importESModule(
 				`chrome://zotero/content/zotero-autocomplete.mjs`
 			);
+			
 			ZoteroAutoComplete.init();
 
+			const { OptionsAutoComplete } = ChromeUtils.importESModule(
+				`chrome://zotero/content/modules/optionsAutoComplete.mjs`
+			);
+			
+			OptionsAutoComplete.init();
+
 			await Zotero.Users.init();
 			await Zotero.Libraries.init();
 			
diff --git a/chrome/content/zotero/zoteroPane.js b/chrome/content/zotero/zoteroPane.js
index 35135497f2..65521ff6df 100644
--- a/chrome/content/zotero/zoteroPane.js
+++ b/chrome/content/zotero/zoteroPane.js
@@ -7032,30 +7032,30 @@ var ZoteroPane = new function () {
 
 	this.buildFieldTransformMenu = function ({ target, onTransform }) {
 		let doc = target.ownerDocument;
-		let value = target.value;
-		let valueTitleCased = Zotero.Utilities.capitalizeTitle(value, true);
-		let valueSentenceCased = Zotero.Utilities.sentenceCase(value);
+		let values = target.values;
+		let valuesTitleCased = values.map(v => Zotero.Utilities.capitalizeTitle(v, true));
+		let valuesSentenceCased = values.map(v => Zotero.Utilities.sentenceCase(v));
 
 		let menupopup = doc.createXULElement('menupopup');
 
 		let titleCase = doc.createXULElement('menuitem');
 		titleCase.setAttribute('label', Zotero.getString('zotero.item.textTransform.titlecase'));
 		titleCase.addEventListener('command', () => {
-			onTransform(valueTitleCased);
+			onTransform(valuesTitleCased);
 		});
-		titleCase.disabled = valueTitleCased == value;
+		titleCase.disabled = values.every((v, i) => valuesTitleCased[i] === v);
 		menupopup.append(titleCase);
 
 		let sentenceCase = doc.createXULElement('menuitem');
 		sentenceCase.setAttribute('label', Zotero.getString('zotero.item.textTransform.sentencecase'));
 		sentenceCase.addEventListener('command', () => {
-			onTransform(valueSentenceCased);
+			onTransform(valuesSentenceCased);
 		});
-		sentenceCase.disabled = valueSentenceCased == value;
+		sentenceCase.disabled = values.every((v, i) => valuesSentenceCased[i] === v);
 		menupopup.append(sentenceCase);
 
 		Zotero.Utilities.Internal.updateEditContextMenu(menupopup, target);
-
+	
 		return menupopup;
 	};
 };
diff --git a/chrome/locale/en-US/zotero/zotero.ftl b/chrome/locale/en-US/zotero/zotero.ftl
index df65a30cbf..e951c8ab10 100644
--- a/chrome/locale/en-US/zotero/zotero.ftl
+++ b/chrome/locale/en-US/zotero/zotero.ftl
@@ -900,3 +900,18 @@ plugins-blocked-plugin =
     .message = This plugin has been disabled by { -app-name }.
 
 data-dir-unsupported-storage = This can happen if the { -app-name } data directory is in a cloud storage folder (OneDrive, Dropbox, etc.) or on a network share.
+
+item-pane-batch-editing-prompt =
+    .aria-label = Batch editing
+
+item-pane-batch-editing-enable =
+    .label = Enter Batch Edit Mode
+
+item-pane-batch-editing-multiple-values-placeholder = Multiple…
+
+item-pane-batch-editing-no-value = (No value)
+
+item-pane-batch-editing-header = { $count ->
+    [one] Editing { $count } item
+   *[other] Editing { $count } items
+}
diff --git a/chrome/skin/default/zotero/overlay.css b/chrome/skin/default/zotero/overlay.css
index 5ceb25685a..432e0248d1 100644
--- a/chrome/skin/default/zotero/overlay.css
+++ b/chrome/skin/default/zotero/overlay.css
@@ -181,3 +181,26 @@
 	background-color: Highlight;
 	color: HighlightText;
 }
+
+.autocomplete-richlistitem[type="options-ac-value"],
+.autocomplete-richlistitem[type="options-ac-no-value"] {
+	height: auto;
+	min-height: auto;
+}
+
+.autocomplete-richlistitem[type="options-ac-value"] > .ac-title,
+.autocomplete-richlistitem[type="options-ac-no-value"] > .ac-title {
+	height: 2em;
+	min-height: 2em;
+	padding-inline: 8px;
+}
+
+.autocomplete-richlistitem[type="options-ac-value"] > .ac-title > .ac-text-overflow-container,
+.autocomplete-richlistitem[type="options-ac-no-value"] > .ac-title > .ac-text-overflow-container {
+	max-width: 100%;
+	overflow: hidden;
+}
+
+.autocomplete-richlistitem[type="options-ac-no-value"] {
+	color: var(--fill-secondary);
+}
diff --git a/scss/elements/_editableText.scss b/scss/elements/_editableText.scss
index c8eaae0cbb..19df8d0a60 100644
--- a/scss/elements/_editableText.scss
+++ b/scss/elements/_editableText.scss
@@ -1,7 +1,7 @@
 @include comfortable {
 	--editable-text-padding-inline: 4px;
 	--editable-text-padding-block: 4px;
-	
+
 	--editable-text-tight-padding-inline: 4px;
 	--editable-text-tight-padding-block: 2px;
 }
@@ -9,7 +9,7 @@
 @include compact {
 	--editable-text-padding-inline: 4px;
 	--editable-text-padding-block: 1px;
-	
+
 	--editable-text-tight-padding-inline: 3px;
 	--editable-text-tight-padding-block: 1px;
 }
@@ -26,10 +26,10 @@ editable-text {
 
 	// Fun auto-sizing approach from CSSTricks:
 	// https://css-tricks.com/the-cleanest-trick-for-autogrowing-textareas/
-	
+
 	display: grid;
 	scrollbar-color: var(--color-scrollbar) var(--color-scrollbar-background);
-	
+
 	&:not([nowrap])::after {
 		content: attr(value) ' ';
 		visibility: hidden;
@@ -39,7 +39,7 @@ editable-text {
 		line-height: inherit;
 		overflow: hidden;
 	}
-	
+
 	&:not([nowrap])::after, &:not([nowrap]) .input {
 		grid-area: 1 / 1 / 2 / 2;
 		overflow-wrap: anywhere;
@@ -56,10 +56,10 @@ editable-text {
 			scrollbar-gutter: stable;
 		}
 	}
-	
+
 	.input {
 		border-radius: 5px;
-		
+
 		// No focus ring for read-only fields
 		&:read-only {
 			--width-focus-border: 0px;
@@ -80,7 +80,7 @@ editable-text {
 		}
 		// Necessary for consistent padding, even if it's actually an <input>
 		-moz-default-appearance: textarea;
-		
+
 		min-height: calc(var(--line-height) * var(--min-visible-lines));
 		margin: 0;
 		border: 1px solid transparent;
@@ -89,13 +89,13 @@ editable-text {
 		line-height: inherit;
 		color: inherit;
 		padding: var(--editable-text-padding-block) var(--editable-text-padding-inline);
-	
+
 		&:read-only, &:not(:focus) {
 			appearance: none;
 			background: transparent;
 			text-align: inherit;
 		}
-		
+
 		&:hover:not(:read-only, :focus) {
 			background: var(--fill-quinary);
 			box-shadow: 0 0 0 1px var(--fill-quinary);
@@ -104,7 +104,7 @@ editable-text {
 		&:focus:not(:read-only) {
 			background: var(--material-background);
 		}
-		
+
 		::placeholder {
 			color: var(--fill-tertiary);
 		}
@@ -120,11 +120,12 @@ editable-text {
 	&[hidden] {
 		display: none;
 	}
+
 	textarea {
 		// Per https://stackoverflow.com/a/22700700, somehow this removes an extra half-line
 		// at the bottom of textarea on all platforms with non-overlay scrollbars
 		overflow-x: hidden;
-		
+
 		// Match the gutters we apply to ::after
 		overflow-y: scroll;
 	}
diff --git a/scss/elements/_itemPane.scss b/scss/elements/_itemPane.scss
index 2dd29f22ef..66316b8abc 100644
--- a/scss/elements/_itemPane.scss
+++ b/scss/elements/_itemPane.scss
@@ -29,4 +29,8 @@ item-pane {
 			width: 100%;
 		}
 	}
+	
+	#batch-edit-prompt-message {
+		padding: 3px 8px;
+	}
 }
diff --git a/scss/elements/_itemPaneHeader.scss b/scss/elements/_itemPaneHeader.scss
index 153b632a84..6d702a8825 100644
--- a/scss/elements/_itemPaneHeader.scss
+++ b/scss/elements/_itemPaneHeader.scss
@@ -78,4 +78,13 @@ item-pane-header {
 		border: none;
 		height: 24px;
 	}
+
+	&.batch-edit.has-custom-head .custom-head {
+		description {
+			font-weight: 600;
+			line-height: 1.333;
+			margin: 0;
+			padding-inline: calc(var(--editable-text-tight-padding-inline) + 1px);
+		}
+	}
 }
diff --git a/test/tests/itemPaneTest.js b/test/tests/itemPaneTest.js
index ce9afb8a78..f3a9fea2d0 100644
--- a/test/tests/itemPaneTest.js
+++ b/test/tests/itemPaneTest.js
@@ -2596,4 +2596,569 @@ describe("Item pane", function () {
 			await waitForToggle('reader toolbar');
 		});
 	});
+	
+	describe("Batch Edit", function () {
+		let createdItems = [];
+		let _createDataObject = async (...args) => {
+			let item = await createDataObject(...args);
+			createdItems.push(item);
+			return item;
+		};
+		afterEach(async function () {
+			for (let item of createdItems.reverse()) {
+				await item.eraseTx();
+			}
+			createdItems = [];
+		});
+
+		it("should enter and exit batch edit mode", async function () {
+			let item1 = await _createDataObject('item', { itemType: 'journalArticle' });
+			let item2 = await _createDataObject('item', { itemType: 'journalArticle' });
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+			await waitForFrame();
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			// Enter batch edit mode
+			assert.equal(itemPane.mode, "batch-edit-prompt");
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			assert.ok(batchEditEnableBtn, "Enter Batch Edit Mode button should exist");
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			// Should now be in item mode with batch editing enabled
+			assert.equal(itemPane.mode, "item");
+
+			// Header should hide title-head and show items selected label
+			let header = itemDetails._header;
+			assert.ok(header.classList.contains('no-title-head'), "title-head should be hidden in batch edit mode");
+			assert.ok(header.querySelector('[data-l10n-id="item-pane-batch-editing-header"]'), "batch editing header label should be in header");
+
+			// Exit batch edit mode by changing selection to a single item
+			await ZoteroPane.selectItem(item1.id);
+			await waitForFrame();
+
+			// Should be back in batch-edit-prompt mode when re-selecting both
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+			await waitForFrame();
+			assert.equal(itemPane.mode, "batch-edit-prompt");
+		});
+		it("should restore collapsed info section state after exiting batch edit via selection change", async function () {
+			let item1 = await _createDataObject('item', { itemType: 'journalArticle' });
+			let item2 = await _createDataObject('item', { itemType: 'journalArticle' });
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			// Select item1 and collapse the info section
+			await ZoteroPane.selectItem(item1.id);
+			await waitForFrame();
+			let infoSection = itemDetails.querySelector('collapsible-section[data-pane="info"]');
+			infoSection.open = false;
+			assert.isFalse(infoSection.open, "info section should be collapsed");
+
+			// Select both items to enter batch edit prompt
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+			await waitForFrame();
+			assert.equal(itemPane.mode, "batch-edit-prompt");
+
+			// Enter batch edit mode
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+			assert.equal(itemPane.mode, "item");
+
+			// Info section should be forced open with no twisty
+			infoSection = itemDetails.querySelector('collapsible-section[data-pane="info"]');
+			assert.isTrue(infoSection.open, "info section should be open in batch edit mode");
+			let twisty = infoSection.querySelector('.twisty');
+			assert.isTrue(twisty.hidden, "twisty should be hidden in batch edit mode");
+
+			// Change selection to just one item -- exits batch edit
+			await ZoteroPane.selectItem(item1.id);
+			await waitForFrame();
+
+			// Info section should restore its previous collapsed state
+			infoSection = itemDetails.querySelector('collapsible-section[data-pane="info"]');
+			assert.isFalse(infoSection.open, "info section should be collapsed after exiting batch edit");
+			twisty = infoSection.querySelector('.twisty');
+			assert.isFalse(twisty.hidden, "twisty should be visible after exiting batch edit");
+		});
+		it("should apply autocomplete value to all items in batch edit mode", async function () {
+			let sharedTitle = "Journal of Shared Research";
+			let differentTitle = "Journal of Different Research";
+
+			let item1 = await _createDataObject('item', { itemType: 'journalArticle' });
+			item1.setField('publicationTitle', sharedTitle);
+			await item1.saveTx();
+
+			let item2 = await _createDataObject('item', { itemType: 'journalArticle' });
+			item2.setField('publicationTitle', sharedTitle);
+			await item2.saveTx();
+
+			let item3 = await _createDataObject('item', { itemType: 'journalArticle' });
+			item3.setField('publicationTitle', differentTitle);
+			await item3.saveTx();
+
+			let item4 = await _createDataObject('item', { itemType: 'journalArticle' });
+			await item4.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id, item3.id, item4.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+			
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+			
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+			let pubTitleField = itemBox.querySelector('editable-text[fieldname="publicationTitle"]');
+			assert.ok(pubTitleField, "publicationTitle field should exist");
+			
+			pubTitleField._ignoredWindowInactiveBlur = false;
+			await activateZoteroPane();
+			await Zotero.Promise.delay(50);
+			pubTitleField.focus();
+
+			// 2 value options + 1 "no value" option
+			await waitForCallback(() => pubTitleField.ref.mController.matchCount === 3, 100, 10);
+			let controller = pubTitleField.ref.mController;
+			// options should be sorted alphabetically, empty values are ignored
+			assert.equal(controller.matchCount, 3);
+			assert.equal(controller.getValueAt(0), `[1] ${differentTitle}`);
+			assert.equal(controller.getFinalCompleteValueAt(0), differentTitle);
+			assert.equal(controller.getValueAt(1), `[2] ${sharedTitle}`);
+			assert.equal(controller.getFinalCompleteValueAt(1), sharedTitle);
+			// Last option should be "no value"
+			assert.equal(controller.getStyleAt(2), 'options-ac-no-value');
+
+			let modifyPromise = waitForItemEvent('modify');
+			pubTitleField.ref.dispatchEvent(new KeyboardEvent(
+				'keydown', { key: "ArrowDown", code: 'ArrowDown', keyCode: KeyboardEvent.DOM_VK_DOWN, bubbles: true, }
+			));
+			await Zotero.Promise.delay(50);
+			pubTitleField.ref.dispatchEvent(new KeyboardEvent(
+				'keydown', { key: "Enter", code: "Enter", keyCode: KeyboardEvent.DOM_VK_RETURN, bubbles: true }
+			));
+			await modifyPromise;
+
+			assert.equal(item1.getField('publicationTitle'), differentTitle);
+			assert.equal(item2.getField('publicationTitle'), differentTitle);
+			assert.equal(item3.getField('publicationTitle'), differentTitle);
+			assert.equal(item4.getField('publicationTitle'), differentTitle);
+		});
+
+		it("should not show View Online button for URL and DOI fields in batch edit mode", async function () {
+			let item1 = await _createDataObject('item', { itemType: 'journalArticle' });
+			item1.setField('url', 'https://example.com/1');
+			item1.setField('DOI', '10.1234/test1');
+			await item1.saveTx();
+
+			let item2 = await _createDataObject('item', { itemType: 'journalArticle' });
+			item2.setField('url', 'https://example.com/2');
+			item2.setField('DOI', '10.1234/test2');
+			await item2.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+
+			let urlLink = itemBox.querySelector('#itembox-field-url-link');
+			let doiLink = itemBox.querySelector('#itembox-field-DOI-link');
+
+			// View Online buttons should be hidden in batch edit mode
+			assert.ok(urlLink.hidden, "URL View Online button should be hidden in batch edit mode");
+			assert.ok(doiLink.hidden, "DOI View Online button should be hidden in batch edit mode");
+		});
+
+		it("should not show date field status or tooltip in batch edit mode", async function () {
+			let item1 = await _createDataObject('item', { itemType: 'journalArticle' });
+			item1.setField('date', '2024-01-15');
+			await item1.saveTx();
+
+			let item2 = await _createDataObject('item', { itemType: 'journalArticle' });
+			item2.setField('date', '2023-06-20');
+			await item2.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+
+			// Date field status indicator (y m d) should not be present
+			let dateStatus = itemBox.querySelector('#zotero-date-field-status');
+			assert.isNull(dateStatus, "date field status should not be present in batch edit mode");
+
+			// Date field should not have a tooltip
+			let dateField = itemBox.querySelector('editable-text[fieldname="date"]');
+			assert.ok(dateField, "date field should exist");
+			assert.isNull(dateField.getAttribute('tooltiptext'), "date field should not have a tooltip in batch edit mode");
+		});
+
+		it("should show union of fields from all item types in cross-type batch edit", async function () {
+			let item1 = await _createDataObject('item', { itemType: 'book' });
+			item1.setField('publisher', 'Test Publisher');
+			await item1.saveTx();
+
+			let item2 = await _createDataObject('item', { itemType: 'audioRecording' });
+			item2.setField('label', 'Test Label');
+			await item2.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+
+			// Shared base field 'publisher' should appear (book: publisher, audioRecording: label)
+			let publisherField = itemBox.querySelector('editable-text[fieldname="publisher"]');
+			assert.ok(publisherField, "publisher (base field) should appear");
+
+			// Shared base field 'medium' should appear (book: format, audioRecording: audioRecordingFormat)
+			let mediumField = itemBox.querySelector('editable-text[fieldname="medium"]');
+			assert.ok(mediumField, "medium (base field) should appear");
+
+			// Book-only fields should appear
+			let editionField = itemBox.querySelector('editable-text[fieldname="edition"]');
+			assert.ok(editionField, "edition (book-only) should appear");
+
+			// audioRecording-only fields should appear
+			let runningTimeField = itemBox.querySelector('editable-text[fieldname="runningTime"]');
+			assert.ok(runningTimeField, "runningTime (audioRecording-only) should appear");
+		});
+		it("should use base field label when field is shared across types, type-specific label otherwise", async function () {
+			let item1 = await _createDataObject('item', { itemType: 'book' });
+			await item1.saveTx();
+
+			let item2 = await _createDataObject('item', { itemType: 'audioRecording' });
+			await item2.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+
+			// Shared field 'publisher' should use base field label
+			let publisherLabel = itemBox.querySelector('#itembox-field-publisher-label');
+			assert.ok(publisherLabel, "publisher label should exist");
+			assert.equal(publisherLabel.textContent, Zotero.ItemFields.getLocalizedString('publisher'));
+
+			// audioRecording-only field 'runningTime' should use type-specific label
+			let runningTimeLabel = itemBox.querySelector('#itembox-field-runningTime-label');
+			assert.ok(runningTimeLabel, "runningTime label should exist");
+			assert.equal(runningTimeLabel.textContent, Zotero.ItemFields.getLocalizedString('runningTime'));
+		});
+		it("should show 'Multiple' placeholder for shared base-mapped fields with different values across types", async function () {
+			let item1 = await _createDataObject('item', { itemType: 'book' });
+			item1.setField('publisher', 'Book Publisher');
+			await item1.saveTx();
+
+			let item2 = await _createDataObject('item', { itemType: 'audioRecording' });
+			item2.setField('label', 'Audio Label');
+			await item2.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+			let publisherField = itemBox.querySelector('editable-text[fieldname="publisher"]');
+			assert.ok(publisherField, "publisher field should exist");
+			assert.isTrue(publisherField.multipleValues, "publisher should show multiple values");
+			assert.equal(
+				publisherField.placeholder,
+				Zotero.getString('item-pane-batch-editing-multiple-values-placeholder')
+			);
+		});
+		it("should apply value to base-mapped fields across different item types", async function () {
+			let item1 = await _createDataObject('item', { itemType: 'book' });
+			item1.setField('publisher', 'Old Publisher');
+			await item1.saveTx();
+
+			let item2 = await _createDataObject('item', { itemType: 'audioRecording' });
+			item2.setField('label', 'Old Label');
+			await item2.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+			let publisherField = itemBox.querySelector('editable-text[fieldname="publisher"]');
+
+			// Simulate editing the field
+			publisherField._ignoredWindowInactiveBlur = false;
+			await activateZoteroPane();
+			await Zotero.Promise.delay(50);
+			publisherField.focus();
+			await Zotero.Promise.delay(50);
+
+			// Type a new value
+			let modifyPromise = waitForItemEvent('modify');
+			publisherField.value = 'New Shared Publisher';
+			publisherField.blur();
+			await modifyPromise;
+
+			// Both items should have the new value in their type-specific fields
+			assert.equal(item1.getField('publisher'), 'New Shared Publisher', "book publisher should be updated");
+			assert.equal(item2.getField('label'), 'New Shared Publisher', "audioRecording label should be updated");
+		});
+		it("should skip items when setting a type-specific field that doesn't apply to all items", async function () {
+			let item1 = await _createDataObject('item', { itemType: 'audioRecording' });
+			item1.setField('runningTime', '3:45');
+			await item1.saveTx();
+
+			let item2 = await _createDataObject('item', { itemType: 'book' });
+			await item2.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+			let runningTimeField = itemBox.querySelector('editable-text[fieldname="runningTime"]');
+			assert.ok(runningTimeField, "runningTime field should exist");
+
+			// Simulate editing the field
+			runningTimeField._ignoredWindowInactiveBlur = false;
+			await activateZoteroPane();
+			await Zotero.Promise.delay(50);
+			runningTimeField.focus();
+			await Zotero.Promise.delay(50);
+
+			// Type a new value -- should not throw for book
+			let modifyPromise = waitForItemEvent('modify');
+			runningTimeField.value = '5:00';
+			runningTimeField.blur();
+			await modifyPromise;
+
+			assert.equal(item1.getField('runningTime'), '5:00', "audioRecording runningTime should be updated");
+			// Book should be unaffected -- no error thrown
+		});
+		it("should show 'Multiple' for Added By in group library batch edit with different users", async function () {
+			let group = await createGroup();
+			await Zotero.Users.setName(1, 'User One');
+			await Zotero.Users.setName(2, 'User Two');
+
+			let item1 = createUnsavedDataObject('item', { libraryID: group.libraryID });
+			item1.setField('createdByUserID', 1);
+			await item1.saveTx();
+
+			let item2 = createUnsavedDataObject('item', { libraryID: group.libraryID });
+			item2.setField('createdByUserID', 2);
+			await item2.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+
+			// "Added By" field should show "Multiple..." placeholder
+			let addedByRow = itemBox.querySelector('.meta-label[fieldname="addedBy"]');
+			assert.ok(addedByRow, "addedBy row should exist");
+			let addedByValue = addedByRow.parentElement.querySelector('editable-text');
+			assert.isTrue(addedByValue.multipleValues, "addedBy should have multipleValues");
+			assert.equal(
+				addedByValue.placeholder,
+				Zotero.getString('item-pane-batch-editing-multiple-values-placeholder'),
+				"addedBy should show Multiple placeholder"
+			);
+			assert.equal(addedByValue.value, '', "addedBy value should be empty");
+
+			// Should not be focusable
+			assert.equal(addedByValue.ref.tabIndex, -1, "addedBy tabIndex should be -1");
+
+			// Group erasure cascades to items
+			await group.eraseTx();
+		});
+		it("should show user name for Added By in group library batch edit when all items have the same user", async function () {
+			let group = await createGroup();
+			await Zotero.Users.setName(1, 'Same User');
+
+			let item1 = createUnsavedDataObject('item', { libraryID: group.libraryID });
+			item1.setField('createdByUserID', 1);
+			await item1.saveTx();
+
+			let item2 = createUnsavedDataObject('item', { libraryID: group.libraryID });
+			item2.setField('createdByUserID', 1);
+			await item2.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+
+			// "Added By" field should show the user name
+			let addedByRow = itemBox.querySelector('.meta-label[fieldname="addedBy"]');
+			assert.ok(addedByRow, "addedBy row should exist");
+			let addedByValue = addedByRow.parentElement.querySelector('editable-text');
+			assert.equal(addedByValue.value, 'Same User', "addedBy should show user name");
+			assert.isTrue(addedByValue.multipleValues, "addedBy should have multipleValues for non-focusable behavior");
+			assert.equal(addedByValue.ref.tabIndex, -1, "addedBy tabIndex should be -1");
+
+			await group.eraseTx();
+		});
+		it("should transform title case for all items in batch edit mode", async function () {
+			let titleCaseTitle = "The Great Gatsby";
+			let sentenceCaseTitle = "to kill a mockingbird";
+
+			// Create two books with different titles in different cases
+			let item1 = await _createDataObject('item', { itemType: 'book' });
+			item1.setField('title', titleCaseTitle);
+			await item1.saveTx();
+
+			let item2 = await _createDataObject('item', { itemType: 'book' });
+			item2.setField('title', sentenceCaseTitle);
+			await item2.saveTx();
+
+			await ZoteroPane.selectItems([item1.id, item2.id]);
+
+			let itemPane = win.ZoteroPane.itemPane;
+			let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+			let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+			batchEditEnableBtn.click();
+			await itemDetails._renderPromise;
+
+			// Find the title field
+			let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+			let titleField = itemBox.querySelector('editable-text[fieldname="title"]');
+			assert.ok(titleField, "title field should exist");
+
+			// Find and click the options button for the title field
+			let optionsButton = itemBox.querySelector('#itembox-field-title-options');
+			assert.ok(optionsButton, "options button should exist");
+
+			// Click the options button to open the context menu
+			let menuPromise = new Promise((resolve) => {
+				let observer = new MutationObserver((mutations) => {
+					for (let mutation of mutations) {
+						for (let node of mutation.addedNodes) {
+							if (node.tagName === 'menupopup') {
+								observer.disconnect();
+								resolve(node);
+							}
+						}
+					}
+				});
+				observer.observe(itemBox.querySelector('#info-box > popupset'), { childList: true });
+			});
+
+			optionsButton.click();
+			let menupopup = await menuPromise;
+
+			let titleCaseMenuItem = Array.from(menupopup.querySelectorAll('menuitem'))
+				.find(item => item.getAttribute('label') === Zotero.getString('zotero.item.textTransform.titlecase'));
+			assert.ok(titleCaseMenuItem, "title case menu item should exist");
+
+			let modifyPromise = waitForItemEvent('modify');
+			titleCaseMenuItem.click();
+			// Label should not flash individual values -- it stays as "Multiple" in batch mode
+			assert.equal(titleField.value, '', "title field value should remain empty in batch mode");
+			assert.equal(titleField.placeholder, 'Multiple\u2026', "title field should still show Multiple placeholder");
+			await modifyPromise;
+
+			assert.equal(item1.getField('title'), "The Great Gatsby", "item1 should remain in title case");
+			assert.equal(item2.getField('title'), "To Kill a Mockingbird", "item2 should be transformed to title case");
+		});
+	});
+
+	it("should not focus read-only fields with multiple values", async function () {
+		let item1 = await createDataObject('item', { itemType: 'journalArticle' });
+		item1.setField('title', 'Item 1');
+		await item1.saveTx();
+
+		let item2 = await createDataObject('item', { itemType: 'journalArticle' });
+		item2.setField('title', 'Item 2');
+		await item2.saveTx();
+		
+		await ZoteroPane.selectItems([item1.id, item2.id]);
+
+		let itemPane = win.ZoteroPane.itemPane;
+		let itemDetails = ZoteroPane.itemPane._itemDetails;
+
+		let batchEditEnableBtn = itemPane.querySelector('button[label="Enter Batch Edit Mode"]');
+		batchEditEnableBtn.click();
+		await itemDetails._renderPromise;
+
+		let itemBox = itemPane.querySelector('#zotero-editpane-info-box');
+		let dateModifiedField = itemBox.querySelector('editable-text[fieldname="dateModified"]');
+		assert.ok(dateModifiedField, "dateModified field should exist");
+		assert.isTrue(dateModifiedField.readOnly, "dateModified should be read-only");
+		assert.isTrue(dateModifiedField.multipleValues, "dateModified should have multiple values");
+		assert.equal(
+			dateModifiedField.placeholder,
+			Zotero.getString('item-pane-batch-editing-multiple-values-placeholder')
+		);
+
+		// tabIndex should be -1 to prevent tab navigation
+		assert.equal(dateModifiedField.ref.tabIndex, -1, "tabIndex should be -1");
+
+		// Clicking the field should not focus it
+		await activateZoteroPane();
+		await Zotero.Promise.delay(50);
+		dateModifiedField.ref.dispatchEvent(new MouseEvent('mousedown', { bubbles: true }));
+		await waitForFrame();
+
+		assert.isFalse(dateModifiedField.focused, "read-only multiple-values field should not be focusable via click");
+		assert.equal(
+			dateModifiedField.placeholder,
+			Zotero.getString('item-pane-batch-editing-multiple-values-placeholder'),
+			"Multiple placeholder should not be cleared"
+		);
+		await item2.eraseTx();
+		await item1.eraseTx();
+	});
 });