/* Decrease the minimum width of the tab sidebar */
@media (-moz-bool-pref: "uc.sidebar.compact-min-width") and (-moz-bool-pref: "zen.view.sidebar-expanded") {  
   #navigator-toolbox {
     --zen-navigation-toolbar-min-width: 115px !important;
  }
}

/* Decrease the minimum height of tabs */
@media (-moz-bool-pref: "uc.sidebar.compact-tabs") {
  .tabbrowser-tab {
    --tab-min-width: 20px !important;
  }
}