mobile-config-firefox/chrome/selected_tab_as_urlbar.css

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

/* This is a horrible hack and absolutely requires click_selected_tab_to_focus_urlbar.css to work. In general it's pertty bad, but meh */

/* Also hides the nav-bar and shows main menu button next to window controls. And makes the selected tab expand a whole bunch  */

/* Whole bunch of z-indexing */
#main-window > body > box{ position: relative; z-index: 1 }
.urlbar-input-box{ z-index: -1 !important; }
#urlbar{ z-index: auto !important; }
#alltabs-button,
#PanelUI-button,
#nav-bar-overflow-button{ z-index: 2; position: relative }

:root[sizemode="normal"] #urlbar-container{ margin-inline: 40px !important; }

#urlbar-input-container > :not(.urlbar-input-box){ opacity: 0 }

#urlbar-background{
  background: transparent !important;
  border: none !important;
  box-shadow: none !important;
}
.urlbarView{
  background: var(--toolbar-field-focus-background-color);
  border: 1px solid var(--toolbar-field-focus-border-color) !important;
  z-index: 1;
  padding: 6px;
  border-radius: 6px;
  box-shadow: 0 0 26px #444;
  left: 50vw;
  margin-left: -50% !important;
}

.tabbrowser-tab[selected][fadein]{ max-width: 100vw !important; min-width: 200px !important }

#navigator-toolbox:focus-within .tabbrowser-tab[selected] .tab-content{
  opacity: 0;
}
#navigator-toolbox:focus-within .tab-background[selected]{
  background-image: -moz-element(#urlbar-input) !important;
  background-position: calc(var(--tab-inline-padding,4px) + 6px) 3px !important;
  background-color: var(--toolbar-field-focus-background-color) !important;
  background-size: auto !important;
}

:root:not([customizing]) #titlebar{ margin-bottom: -40px }

/* Oh and! also hide other buttons from the nav-bar because why not */
#nav-bar-customization-target > :not(#urlbar-container){ visibility: collapse }
#TabsToolbar > .toolbar-items{ margin-right: 40px !important; }

#nav-bar{ 
  padding-right: 138px;
  box-shadow: none !important;
  background-color: transparent !important;
}