helm/users/profiles/firefox/userChrome.css

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

/* Hide main tabs toolbar */
#TabsToolbar {
	visibility: collapse !important;
}

/*** NAV BAR ***/
/* Hide urlbar */
#nav-bar {
	position: relative !important;
	z-index: 2 !important;
	height: 2px !important;
	min-height: 2px !important;
	margin-bottom: -2px !important;
	opacity: 0 !important;
	border: none !important;
}

/* But unfocus it when we invoke it with ctrl+L */
#nav-bar:focus-within {
	height: auto !important;
	margin-bottom: 0px !important;
	opacity: 1 !important;
	overflow: show !important;
}

#urlbar-container {
	min-height: 0 !important;
}

#urlbar {
	top: 0 !important;
}

#urlbar-input-container {
	height: 28px !important;
}

/* hides the sidebar header */
#sidebar-header {
	display: none !important;
}

.tab[selected="true"] {
	visibility: collapse;
}

.tabbrowser-tab {
	visibility: collapse;
}

.tabbrowser-tab[visuallyselected="true"] {
	visibility: collapse;
}

/* Credits to https://github.com/MrOtherGuy for hthe following snippet*/

/* Source file https://github.com/MrOtherGuy/firefox-csshacks/tree/master/chrome/autohide_sidebar.css made available under Mozilla Public License v. 2.0
See the above repository for updates as well as full license text. */

/* Show sidebar only when the cursor is over it */
/* The border controlling sidebar width will be removed so you'll need to modify these values to change width */

#sidebar-box{
  --uc-sidebar-width: 44px; /* Only thing I (gale) changed */
  --uc-sidebar-hover-width: 210px;
  --uc-autohide-sidebar-delay: 600ms; /* Wait 0.6s before hiding sidebar */
  position: relative;
  min-width: var(--uc-sidebar-width) !important;
  width: var(--uc-sidebar-width) !important;
  max-width: var(--uc-sidebar-width) !important;
  z-index:1;
}

#sidebar-box[positionend]{ direction: rtl }
#sidebar-box[positionend] > *{ direction: ltr }

#sidebar-box[positionend]:-moz-locale-dir(rtl){ direction: ltr }
#sidebar-box[positionend]:-moz-locale-dir(rtl) > *{ direction: rtl }

#main-window[sizemode="fullscreen"] #sidebar-box{ --uc-sidebar-width: 1px; }

#sidebar-splitter{ display: none }

#sidebar-header{ overflow: hidden; /*color: var(--chrome-color, inherit) !important*/}

#sidebar{
  transition: min-width 115ms linear var(--uc-autohide-sidebar-delay) !important;
  min-width: var(--uc-sidebar-width) !important;
  will-change: min-width;
}

#sidebar-box:hover > #sidebar{ min-width: var(--uc-sidebar-hover-width) !important; transition-delay: 0ms !important }

.sidebar-panel{
  /*background-color: transparent !important;
  color: var(--newtab-text-primary-color) !important;*/
}

.sidebar-panel #search-box{
  -moz-appearance: none !important;
  /*background-color: rgba(249,249,250,0.1) !important; 
  color: inherit !important;
	*/
}

/* Add sidebar divider and give it background */

#sidebar,
#sidebar-header{
  /*background-color: inherit !important;*/
  border-inline: 1px solid rgb(80,80,80);
  border-inline-width: 0px 1px;
}

#sidebar-box:not([positionend]) > :-moz-locale-dir(rtl),
#sidebar-box[positionend] > *{
  border-inline-width: 1px 0px;
}

/* Move statuspanel to the other side when sidebar is hovered so it doesn't get covered by sidebar */

#sidebar-box:not([positionend]):hover ~ #appcontent #statuspanel{ inset-inline: auto 0px !important; }
#sidebar-box:not([positionend]):hover ~ #appcontent #statuspanel-label{ margin-inline: 0px !important; border-left-style: solid !important; }