librewolf/chrome/userChrome.css

   1 /* hide tabs */
   2 #main-window[tabsintitlebar="true"]:not([extradragspace="true"]):not([customizing]) #tabbrowser-tabs,
   3 #main-window[tabsintitlebar="true"]:not([extradragspace="true"]):not([customizing]) #alltabs-button,
   4 /* hide tst header */
   5 #main-window:not([customizing]) #sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] > #sidebar-header {
   6     visibility: collapse !important;
   7 }