Firefox Quantum UserChrome.css (LessChrome HD)

userchrome.css

/*
 * Do not remove the @namespace line -- it's required for correct functioning
 */
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */

#nav-bar{
	margin-top: -32px;
	visibility: hidden;
	transition:0s all 2s;
}

#TabsToolbar:active ~ #nav-bar, #nav-bar:hover{
	margin-top: 0px;
	visibility: visible;
	transition:0s all 0s;
}

.tabbrowser-tabs {
    display: inline-block;
    text-align: center;
	width:auto;
}

/*
.tabbrowser-tab {
    display: contents;
}*/

/*.tab-label-container,*/ .titlebar-placeholder{
	display:none !important;
}