mobile-config-firefox/chrome/combined_tabs_and_main_toolbars.css

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

/* Combines tabs toolbar and nav-bar in such a way that opening new tabs will reserve
   space from nav-bar. Only pinned tabs and the selected tab will be visible, all other tabs need to be accessed via alltabs-button or shortcut keys */

/* You WILL NEED either autohide_menubar.css or overlay_menubar.css with this or use custom css that does something similar */  

#toolbar-menubar[autohide="true"] > .titlebar-buttonbox-container{ display: none !important; }
#toolbar-menubar{ left:0 }

@supports -moz-bool-pref("layout.css.osx-font-smoothing.enabled"){
  #TabsToolbar > .titlebar-buttonbox-container{
    position: fixed;
    display: block;
    left: 0px;
    z-index: 1;
  }
  :root[tabsintitlebar="true"] #nav-bar{ padding-inline: calc(var(--uc-hide-window-control-space,1) * 96px + 20px) 0px !important; }
  
  @media (-moz-os-version: windows-win10){
    :root[tabsintitlebar="true"] #nav-bar{ padding-left: calc(var(--uc-hide-window-control-space,1) * 134px + 20px) !important; }
  }
  #toolbar-menubar[autohide="true"] + #TabsToolbar .titlebar-buttonbox{ -moz-box-direction: reverse }
}

#navigator-toolbox{ --tab-min-height: 40px }
:root[uidensity="compact"] #navigator-toolbox{ --tab-min-height: 32px }

@media (-moz-os-version: windows-win10){
  :root[sizemode="maximized"] > body > box{ margin-top: 8px }
}

#navigator-toolbox{
  display: flex;
  flex-direction: row-reverse;
  flex-wrap: wrap;
}

#titlebar{ -moz-appearance: none !important; }
:root[tabsintitlebar="true"] #nav-bar{ padding-left: 20px }

#nav-bar,#PersonalToolbar{ flex-grow: 1; }

/* This margin on bookmarks toolbar makes absolutely no sense, but it won't work properly without it */
.browser-toolbar.chromeclass-directories:not([collapsed="true"]){
  min-width: 100vw !important;
  margin-bottom: var(--tab-min-height);
}
/* reduce urlbar minimum width before things start to go to overflow menu */
#urlbar-container{ min-width: 300px !important; }

#TabsToolbar > .titlebar-spacer[type="pre-tabs"]{ display: none !important; }
#alltabs-button{ display: -moz-box !important }
/* If you are only working with just a few tabs then you may safely delete the following to allow non-pinned tabs to be shown */
.tabbrowser-tab:not([pinned]):not([selected]){ visibility: collapse }