UserChrome autohide ff75

userChrome.css

#navigator-toolbox {
  -moz-appearance: none;
  background-color: #0f111a00 !important;
  border-top: none;
}
.browser-toolbar:not(.titlebar-color),
#tabbrowser-tabs:not([movingtab])
  > .tabbrowser-arrowscrollbox
  > .tabbrowser-tab
  > .tab-stack
  > .tab-background[multiselected='true']:-moz-lwtheme,
#tabbrowser-tabs:not([movingtab])
  > .tabbrowser-arrowscrollbox
  > .tabbrowser-tab
  > .tab-stack
  > .tab-background[selected='true']:-moz-lwtheme,
box {
  background-color: #0f111a !important;
  background-image: none !important;
}
* {
  --tab-line-color: #ff5370;
  --tab-min-width: 76px;
}

#urlbar:not(.megabar):not([focused='true']):-moz-lwtheme,
#urlbar.megabar:not([focused='true']):-moz-lwtheme > #urlbar-background,
#navigator-toolbox #searchbar:not(:focus-within):-moz-lwtheme,
#navigator-toolbox {
  border: none !important;
}
#urlbar:not(.megabar):-moz-lwtheme,
#urlbar.megabar:-moz-lwtheme > #urlbar-background,
#navigator-toolbox #searchbar:-moz-lwtheme {
  background-color: #0f111a !important;
}
#navigator-toolbox {
  --tabs-border-color: #0f111a !important;
}

toolbox {
  z-index: 10;
  margin-top: 0px !important;
  margin-bottom: -30px !important;
  height: 0 !important;
}

#nav-bar {
  opacity: 0;
  transition: opacity 0.2s ease-in-out !important;
}

:hover > toolbox,
toolbox:focus-within {
  opacity: 1;
  transition: opacity 0.2s ease-in-out !important ;
}
:hover > #nav-bar,
toolbox:focus-within > #nav-bar {
  opacity: 1;
  background-color: #0f111a !important;
}