FirefoxSidebar/prefs.css

:root {
  --sidebar-width: 50px;
  --toolbar-height: -50px;
  --menubar-height: -74px;
  --sidebar-padding: calc(var(--sidebar-width) + 5px);
  --toolbar-start-end-padding: 5px !important;

  /*
    Uncomment this if you want a custom sidebar header color,
    this shouldn't be needed anymore but might be!
  */
  /* --custom-sidebar-bg: #000 !important; */

  /* ====== Extension Settings ====== */

  /* === Window Control / Client Side Display Settings === */
  --csd-width: 100px;
  --csd-top: 6px;

  /*
    If you are putting this on the left or right side uncomment the side
    preferences below and comment the other
  */

  /* 
    Left Side
    Default: --csd-left: 50px; --csd-margin-left: 92px;
  */
  /*
  --csd-left: 50px;
  --csd-margin-left: 92px;
  */
  /* ====== */

  /*
    Right Side
    Defaults: --csd-right: 0px; --csd-margin-right: 95px;
  */

  --csd-right: 0px;
  --csd-margin-right: 95px;

  /* ====== */

  /* === END: Window Control / Client Side Display Settings === */
}