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

/* Hide sidebar with one tab */
#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] {
    transition: all 0.2s ease;
}
#main-window:not([customizing])
  #sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"]:not(:has([data-current-uri="about:newtab"])):not(:hover) {
    z-index: 2 !important;
    overflow: hidden;
    min-width: 2px !important;
    max-width: 2px !important;
}