:root {
    --sidebar-width: 180px;
    --toolbar-height: -26px;
    --menubar-height: -60px;
    --toolmenubar-height: -85px; /* sum of previous two */
  }

 /* Remove tabs toolbar to save space */
#TabsToolbar {
     visibility: collapse !important;
}

/* Hide sidebar header, when using Tree Style Tab. */
#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] #sidebar-header {
    visibility: collapse;
}

/* Hide splitter, when using Tree Style Tab. */
#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] + #sidebar-splitter {
    display: none !important;
}

/* lock sidebar to height by doing the inverse margin of the toolbar element */
#sidebar-box {
    z-index: 1000 !important;
    position: relative!important;
    margin-top: var(--menubar-height) !important;
    border-right: 1px solid #ccc;
  }

  #main-window[title^="Firefox Nightly"] #sidebar-box {
    margin-top: var(--toolmenubar-height) !important;
  }

  /* lock sidebar to specified width */
  #sidebar-box, #sidebar-box #sidebar {
      min-width: var(--sidebar-width) !important;
      max-width: var(--sidebar-width) !important;
  }

  #sidebar { border-right: 1px solid #ccc; }

  #nav-bar {
    padding-top: 5px !important;
    padding-bottom: 5px !important;
    margin-left: var(--sidebar-width) !important;
    padding-left: 7px !important;
  }