Firefox userchrome file, hides tab bar when using vertical tabs

userchrome.css

/*
  Firefox userchrome file, hides tab bar when using vertical tabs

  Save as:
    C:\Users\<username>\AppData\Roaming\Mozilla\Firefox\Profiles\<random giberish>.default-release\chrome\userchrome.css
  Enable Firefox CSS customization feature, which is turned off by default:
    - Enter about:config in the address bar and select "Accept the Risk and Continue."
    - Under "Search preference name," paste the following text: toolkit.legacyUserProfileCustomizations.stylesheets
    - Tap the toggle button on the right so the preference says "true."
*/
.tabbrowser-tab {
  visibility: collapse;
}
.titlebar-button {
  height: 42px !important;
}
#nav-bar {
  margin-top: -42px;
  margin-right: 160px;
  box-shadow: none !important;
}
[uidensity="compact"]:root .titlebar-button {
  height: 32px !important;
}
[uidensity="compact"]:root #nav-bar {
  margin-top: -32px;
}
#titlebar-spacer {
  background-color: var(--chrome-secondary-background-color);
}
#titlebar-buttonbox-container {
  background-color: var(--chrome-secondary-background-color);
}
.titlebar-color {
  background-color: var(--toolbar-bgcolor);
}
/* Hide sidebar in fullscreen: */
/* #main-window[inFullscreen="true"] #sidebar-box,
#main-window[inFullscreen="true"] #sidebar-box + splitter {
  visibility: collapse;
}
#sidebar-box #sidebar-header {
  display: none !important;
} */