zotero/scss/elements/_quickSearchTextbox.scss

// | 6px padding | 16px icon width | 2px padding | 8px dropmarker width | 4px padding |
quick-search-textbox {
	--search-textbox-width: 172px;
	font-size: var(--zotero-font-size);
	margin-right: 0;
	width: var(--search-textbox-width);
	height: 28px;

	*[zoteroFontSize=small] {
		font-size: 11px;
	}

	:is(search-textbox)::part(search-sign),
	:is(search-textbox)::part(search-icon) {
		@include svgicon-menu("magnifier", "universal", "16");
		color: var(--fill-secondary);
		// right: 2px padding + 8px dropmarker width + 4px padding + 6px padding
		// Use explicit left/right padding here because this element is flipped in RTL (see _search.scss)
		padding: 6px 14px 6px 6px;
		margin: 0;
	}
}

#zotero-tb-search-dropmarker {
	position: relative;
	// 6px padding + 16px icon width + 2px padding + 8px dropmarker width + 4px padding
	width: 36px;
	margin-inline-end: -36px;
	z-index: 2;
}

#zotero-tb-search-menu-button {
	width: 36px;
	height: 28px;
	min-height: 28px;
	// 6px padding + 16px icon width + 2px padding
	padding-block: 0;
	padding-inline: 24px 4px;
	margin: 0;
	border: 0;
	border-radius: 5px;
	appearance: none;
	min-width: 0;
	cursor: default;
	@include svgicon-menu("chevron-6", "universal", "8");
	color: var(--fill-secondary);
	background: transparent;

	@include focus-ring;

	.button-menu-dropmarker {
		display: none; /* Hide automatic dropmarker */
	}
}

#zotero-tb-search-textbox {
	padding: 0;
	padding-inline-end: 6px;
	margin: 0;
	position: relative;
	inset-inline-start: 0;
	width: var(--search-textbox-width);
	height: 28px;
	z-index: 1;
}

#zotero-tb-search-spinner {
	margin: 0 8px;
}