Refined find bar (https://www.reddit.com/r/FirefoxCSS/comments/7fxtdm/refined_find_bar_top_right_aligned_animated/)

findbar.css

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

@keyframes scale-in {
	0% {
		transform: scaleY(0);
	}
	100% {
		transform: scaleY(1);
	}
}

@keyframes scale-out {
	0% {
		transform: scaleY(1);
	}
	100% {
		transform: scaleY(0);
	}
}

.browserContainer {
	position: relative;
}

findbar {
	animation: 0.2s scale-in;
	transform-origin: top center;
	background: var(--toolbar-bgcolor) !important;
	padding: 4px 6px 6px 6px;
	border: 1px solid var(--toolbox-border-bottom-color);
	border-top-width: 0;
	border-radius: 0 0 var(--toolbarbutton-border-radius) var(--toolbarbutton-border-radius);
	position: absolute;
	top: -2px;
	right: 38px;
}

findbar[hidden="true"] {
	animation: 0.2s scale-out;
}

findbar .findbar-container {
	padding: 0 !important;
	padding-inline-start: 0 !important;
	padding-inline-end: 0 !important;
}

findbar .findbar-container .findbar-textbox {
	padding: 6px 8px !important;
	background-color: var(--url-and-searchbar-background-color) !important;
	border-color: var(--backbutton-border-color) !important;
}

findbar .findbar-container .findbar-textbox[status="notfound"] {
	background-color: #E74C3C !important;
	color: white !important;
}

findbar .findbar-container .findbar-find-previous,
findbar .findbar-container .findbar-find-next {
	background: transparent !important;
	border-color: var(--backbutton-border-color) !important;
}

findbar .findbar-container .findbar-find-previous:hover, findbar .findbar-container .findbar-find-previous:focus,
findbar .findbar-container .findbar-find-next:hover,
findbar .findbar-container .findbar-find-next:focus {
	background-color: var(--toolbarbutton-hover-background) !important;
}

findbar .findbar-button {
	border: 1px solid var(--backbutton-border-color);
	border-radius: var(--toolbarbutton-border-radius) !important;
}

findbar .findbar-closebutton {
	margin-right: 4px !important;
	padding-inline-end: 0 !important;
	position: relative;
	top: 6px;
}

window[lwtheme="true"] findbar {
	background: var(--lwt-header-image) !important;
	background-attachment: fixed !important;
	background-position: top right !important;
	top: -1px;
}

window[lwtheme="true"] findbar:before {
	display: block;
	content: '';
	position: absolute;
	top: 0;
	left: 0;
	z-index: 0;
	width: 100%;
	height: 100%;
	background-color: var(--toolbar-bgcolor);
}

window[lwtheme="true"] findbar .findbar-container,
window[lwtheme="true"] findbar .findbar-closebutton {
	position: relative;
	z-index: 1;
}

window[lwtheme="true"] findbar .findbar-textbox {
	color: var(--lwt-text-color) !important;
	background-color: var(--toolbar-bgcolor) !important;
}

window[lwtheme="true"] findbar .findbar-textbox[status="notfound"] {
	background-color: #E74C3C !important;
	color: white !important;
}

window[lwtheme="true"] findbar .findbar-button[checked="true"] {
	font-weight: bold;
	background-color: var(--toolbar-bgcolor) !important;
}

window[lwtheme="true"] findbar .findbar-find-status, window[lwtheme="true"] findbar .found-matches {
	color: var(--lwt-text-color) !important;
}

findbar.scss

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

@keyframes scale-in {
	0% { transform: scaleY(0); }
	100% { transform: scaleY(1); }
}

@keyframes scale-out {
	0% { transform: scaleY(1); }
	100% { transform: scaleY(0); }
}

.browserContainer {
	position: relative;
}

$duration: 0.2s;

findbar {
	animation: $duration scale-in;
	transform-origin: top center;
	background: var(--toolbar-bgcolor) !important;
	padding: 4px 6px 6px 6px;
	border: 1px solid var(--toolbox-border-bottom-color);
	border-top-width: 0;
	border-radius: 0 0 var(--toolbarbutton-border-radius) var(--toolbarbutton-border-radius);
	position: absolute;
	top: -2px;
	right: 38px;

	&[hidden="true"] {
		animation: $duration scale-out;
	}

	.findbar-container {
		padding: 0 !important;
		padding-inline-start: 0 !important;
		padding-inline-end: 0 !important;

		.findbar-textbox {
			padding: 6px 8px !important;
			background-color: var(--url-and-searchbar-background-color) !important;
			border-color: var(--backbutton-border-color) !important;

			&[status="notfound"] {
				background-color: #E74C3C !important;
				color: white !important;
			}
		}

		.findbar-find-previous,
		.findbar-find-next {
			background: transparent !important;
			border-color: var(--backbutton-border-color) !important;

			&:hover,
			&:focus {
				background-color: var(--toolbarbutton-hover-background) !important;
			}
		}
	}

	.findbar-button {
		border: 1px solid var(--backbutton-border-color);
		border-radius: var(--toolbarbutton-border-radius) !important;
	}

	.findbar-closebutton {
		margin-right: 4px !important;
		padding-inline-end: 0 !important;
		position: relative;
		top: 6px;
	}
}

window[lwtheme="true"] {
	findbar {
		background: var(--lwt-header-image) !important;
		background-attachment: fixed !important;
		background-position: top right !important;
		top: -1px;

		&:before {
			display: block;
			content: '';
			position: absolute;
			top: 0;
			left: 0;
			z-index: 0;
			width: 100%;
			height: 100%;
			background-color: var(--toolbar-bgcolor);
		}

		.findbar-container,
		.findbar-closebutton {
			position: relative;
			z-index: 1;
		}

		.findbar-textbox {
			color: var(--lwt-text-color) !important;
			background-color: var(--toolbar-bgcolor) !important;

			&[status="notfound"] {
				background-color: #E74C3C !important;
				color: white !important;
			}
		}

		.findbar-button {
			&[checked="true"] {
				font-weight: bold;
				background-color: var(--toolbar-bgcolor) !important;
			}
		}

		.findbar-find-status, .found-matches {
			color: var(--lwt-text-color) !important;
		}
	}
}