@media not (-moz-bool-pref: "zen.view.sidebar-expanded") {
  .tabbrowser-tab:is([soundplaying], [muted]) {
    & .tab-background::after {
      content: "";
      position: absolute;
      width: 4px !important;
      border-radius: 4px !important;
      height: 66.66% !important;
      top: 50%;
      left: calc(100% - 4px) !important;
      transform: translateY(-50%);
      background-color: var(--zen-primary-color) !important;
    }

    &:not([selected="true"]) .tab-background::after {
      height: 33.33% !important;
    }

    &:not([selected="true"]):hover .tab-background::after {
      height: 66.66% !important;
    }
  }
}