I found the indicators too narrow, so I made this CSS change (in TST config):

  /* Better highlighting of tab container */
  .tab {
    padding-right: 12px !important;
  }
  .contextual-identity-marker {
    width: 6px !important;
    border-radius: 2px;
    margin: 2px;
    opacity: 0.75;
  }

Hope it's helpful for someone else :)