🦊 Firefox macOS: Tabs on Bottom & Tab Close Button on Left

userChrome.css

/* Firefox userChrome.css for Mac 
   1) Tabs on Bottom 
   2) Tab Close Button on Left
*/

/* Tabs on Bottom */
/* -------------------------------- */
#TabsToolbar {
  -moz-box-ordinal-group: 2;
}
#nav-bar{
  border-top-width: 0px !important;
}
/*Remove extra tab bar space*/
#TabsToolbar {
  padding-inline-start: 0px !important;
  margin-bottom: none !important;
}
#titlebar-placeholder-on-TabsToolbar-for-captions-buttons {
  display: none;
}
/* Clean up spacing */
.titlebar-placeholder {
  display: none !important;
}
.box-inherit .scrollbox-innerbox {
  margin-right: 0 !important;
}
#TabsToolbar .tabbrowser-arrowscrollbox > .arrowscrollbox-scrollbox {
  padding-inline-start: 0px !important;
  padding-inline-end: 0px !important;
}
/* Position window controls */
#titlebar-buttonbox-container {
  margin-left: 5px !important;
  margin-top: 5px !important;
}
/*
 * Make room for window controls.
 * Only apply this style when not in fullscreen mode.
 */
#main-window:not([inFullscreen]) #nav-bar{
  padding: 0px 5px 0px 90px !important;
}

/* Override vertical shifts when moving a tab (9 Jan 2018) */
#TabsToolbar[movingtab] {
  padding-bottom: 0 !important;
}
#TabsToolbar[movingtab] > .tabbrowser-tabs {
  padding-bottom: 0 !important;
  margin-bottom: 0 !important;
}
#TabsToolbar[movingtab] + #nav-bar {
  margin-top: 0 !important;
}

/* Tab Close Button on Left */
/* -------------------------------- */
#TabsToolbar .tab-close-button { 
  -moz-box-ordinal-group: 0 !important; 
  margin-left: -6px !important;
  border-radius: 2px !important;
  transition: opacity 200ms !important;
}
#TabsToolbar .tab-icon-image:not([pinned])
{
  margin-left: 6px;
}