diff --git a/chrome/content/zotero/elements/quickSearchTextbox.js b/chrome/content/zotero/elements/quickSearchTextbox.js
index 585122d126..5cbde4150d 100644
--- a/chrome/content/zotero/elements/quickSearchTextbox.js
+++ b/chrome/content/zotero/elements/quickSearchTextbox.js
@@ -37,7 +37,7 @@
 					<hbox id="search-wrapper">
 					</hbox>
 					<hbox id="advanced-search-indicator">
-						<label id="advanced-search-label"/>
+						<label id="advanced-search-label" crop="end"/>
 						<toolbarbutton class="zotero-clicky advanced-collapse-button" tabindex="0"/>
 						<toolbarbutton class="zotero-clicky advanced-close-button" data-l10n-id="advanced-search-close" tabindex="0"/>
 					</hbox>
@@ -206,6 +206,7 @@
 					selectedSearchType === 'temporary' ? 'advanced-search' : 'edit-saved-search',
 				);
 				this.deck.selectedIndex = state === 'closed' ? 0 : 1;
+				this.toggleAttribute('advanced-search-open', state !== 'closed');
 				this.querySelector('#advanced-search-indicator').dataset.collapsed = state === 'collapsed';
 				this.querySelector('.advanced-collapse-button').hidden = selectedSearchType === 'saved';
 				document.l10n.setAttributes(
diff --git a/scss/elements/_quickSearchTextbox.scss b/scss/elements/_quickSearchTextbox.scss
index 2c79bcfbd2..cd31a0ae75 100644
--- a/scss/elements/_quickSearchTextbox.scss
+++ b/scss/elements/_quickSearchTextbox.scss
@@ -8,6 +8,38 @@ quick-search-textbox {
 	max-width: 300px;
 	flex-grow: 1;
 
+	// While the Advanced Search indicator is shown, size this element to the indicator's content
+	// (full label + buttons) rather than the 146px quick-search width, and allow shrinking below
+	// it (min-width: 0) only when the toolbar overflows -- so the label stays full on a normal
+	// window and crops just enough on a narrow one, keeping the buttons to its right (collapse/
+	// close and the stacked item-pane toggle) unclipped. The normal search box keeps its default
+	// size (it isn't shown then).
+	&[advanced-search-open] {
+		width: auto;
+		min-width: 0;
+		// Take only the indicator's width (don't grow toward max-width), so the buttons sit right
+		// after the label and the toggle isn't pushed out; the toolbar's spacer absorbs the slack
+		flex-grow: 0;
+
+		// A XUL <deck> sizes to its largest panel and doesn't clamp the panel to the deck's
+		// width, so the indicator keeps its full width and overflows. Since only the indicator
+		// is shown while advanced search is open, lay the deck out as flex and let the indicator
+		// (and its label) shrink, hiding the inactive quick-search panel.
+		#search-deck {
+			min-width: 0;
+			display: flex;
+		}
+
+		#search-wrapper {
+			display: none;
+		}
+
+		#advanced-search-indicator {
+			flex: 1;
+			min-width: 0;
+		}
+	}
+
 	*[zoteroFontSize=small] {
 		font-size: 11px;
 	}
@@ -160,6 +192,9 @@ quick-search-textbox {
 
 	& > label {
 		flex: 1;
+		// Let the label shrink and crop on a narrow window so the collapse/close buttons to its
+		// right stay visible
+		min-width: 0;
 		padding-inline: 4px;
 		font-weight: 700;
 	}