zotero/scss/components/_tabsMenu.scss

#zotero-tabs-menu-wrapper {
	background: var(--material-sidepane);
	padding: 7px;
	border-radius: 5px;
}

#zotero-tabs-menu-filter {
	margin: 0 0 7px 0;
	border-radius: 5px;
	border: 1px solid transparent;
	padding-inline-start: 5px !important;
	padding: 2px;
	@include focus-ring(3px, 5px);
}

#zotero-tabs-menu-list {
	appearance: none;
	margin: 0;

	.zotero-tabs-menu-entry {
		@include focus-ring(3px, 5px);
		border-radius: 6px;
		height: 22px;
		margin: 0;
		&.close {
			width: 22px;
		}
		&.title {
			padding: 0;
			padding-inline-start: 6px;
			color: unset;
			&.selected {
				font-weight: 600;
			}
			description {
				overflow: hidden;
				// override default description margins
				margin-bottom: 0;
				margin-block-start: 0;
			}
			.tab-icon {
				width: 16px;
				height: 16px;
			}
		}
		
		// Using .hover class instead of pseudo element to avoid the 
		// hover effect from sticking around after drag-and-drop
		// https://bugs.webkit.org/show_bug.cgi?id=134555
		&.hover {
			background-color: var(--fill-quinary) !important;
		}
		&:active {
			background-color: var(--fill-quarternary) !important;
		}
	}
	#zotero-tabs-menu-dragged {
		opacity: 0;
	}	
}