firefox-tree-style-tabs-macos

firefox-tree-style-tabs-macos.md

see alexandru - Tree Style Tab gist

/* Compact top bar tabs */

[uidensity="compact"]:root {
  --tab-min-height: 22px !important;
  --newtab-margin: -3px 0 -3px -3px !important;
}

:root[uidensity="compact"] #tabbrowser-tabs {
  --tab-min-height: var(--tab-min-height) !important;
}

.tabbrowser-tab {
  max-height: var(--tab-min-height) !important;
}

.tabs-newtab-button{
  margin: var(--newtab-margin) !important;
}

/* hide tabs from tabs bar */

.tabbrowser-tabs {
  height: 22px !important;
  visibility: collapse;
}

#tabbrowser-tabs {
  visibility: collapse;
  height: 22px !important;
}

/* Hide side bar header */
@-moz-document url("chrome://browser/content/browser.xul") {

  #sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] #sidebar-header {
    visibility: collapse !important;
  }

}