Firefox userChrome.css 2

/* TABS: on bottom */

:root
{
    --uc-titlebar-padding: 0px;
}

:root[sizemode="maximized"][tabsintitlebar]
{
    --uc-titlebar-padding: 8px
}

.titlebar-buttonbox-container
{
    position: fixed;
    display: block;
    top: var(--uc-titlebar-padding,0px);
    right:0;
    height: 40px;
}

/* Mac specific. You should set that font-smoothing pref to true if you are on any platform where window controls are on left */
@supports -moz-bool-pref("layout.css.osx-font-smoothing.enabled")
{
    :root{ --uc-titlebar-padding: 0px !important }
    .titlebar-buttonbox-container{ left:0; right: unset; }
}

:root[uidensity="compact"] .titlebar-buttonbox-container{ height: 32px }

#toolbar-menubar[inactive] > .titlebar-buttonbox-container{ opacity: 0 }

#navigator-toolbox
{
    padding-top: var(--uc-titlebar-padding,0px) !important;
}


.titlebar-buttonbox-container > .titlebar-buttonbox{ height: 100%; }

#titlebar
{
    -moz-box-ordinal-group: 2;
    -moz-appearance: none !important;
}

.titlebar-placeholder,
#TabsToolbar .titlebar-spacer{ display: none; }
/* Also hide the toolbox bottom border which isn't at bottom with this setup */
#navigator-toolbox::after{ display: none !important; }

@media (-moz-gtk-csd-close-button){ .titlebar-button{ -moz-box-orient: vertical } }

/* These exist only for compatibility with autohide-tabstoolbar.css */
toolbox#navigator-toolbox > toolbar#nav-bar.browser-toolbar{ animation: none; }
#navigator-toolbox:hover #TabsToolbar{ animation: slidein ease-out 48ms 1 }




#TabsToolbar
{
    position: absolute !important;
    /*display: block;*/
    bottom: 0 !important;
    width: 100vw !important;
    background-color: var(--toolbar-bgcolor) !important;
}




/* drag space */
.titlebar-spacer[type="pre-tabs"],
.titlebar-spacer[type="post-tabs"] {
  display:none !important;
}

#main-window:not([chromehidden*="toolbar"]) #navigator-toolbox
{
  padding-bottom: var(--tab-min-height) !important;
}

/* TABS: height */
:root {
 --tab-toolbar-navbar-overlap: 0px !important;
 --tab-min-height: 25px !important; /* adjust to suit your needs */
}
:root #tabbrowser-tabs {
 --tab-min-height: 25px !important; /* needs to be the same as above under :root */
 --tab-min-width: 80px !important;
}

#TabsToolbar {
 height: var(--tab-min-height) !important;
 margin-bottom: 1px !important;
 box-shadow: ThreeDShadow 0 -1px inset, -moz-dialog 0 1px !important;
 background-color: var(--toolbar-bgcolor) !important;
}

/* Fixes window moving when moving a tab */
#navigator-toolbox[movingtab] > #titlebar > #TabsToolbar {
  padding-bottom: unset !important;
}
#navigator-toolbox[movingtab] #tabbrowser-tabs {
  padding-bottom: unset !important;
  margin-bottom: unset !important;
}
#navigator-toolbox[movingtab] > #nav-bar {
  margin-top: unset !important;
}

/* Fixes window buttons being on window area */
.titlebar-buttonbox-container{
  position: fixed;
  top:0;
  left:0;
  height: 0px;
}

/* Hides favicons in the bookmarks bar. */
#personal-bookmarks .toolbarbutton-icon
{
  display: none !important;
}