code: public void mark() {
      // ensure it's not marked yet - so a control doesn't contain the same styleClass multiple times
      if (!marked) {
        SimpleControl renderer = (SimpleControl) getField().getRenderer();
        Node markNode = renderer.getFieldLabel();
        markNode.getStyleClass().add(MARKED_STYLE_CLASS);
        markNode.setOnMouseExited(unmarker);
        marked = !marked;
      }
    }
docs: Marks a setting.
  Is used for the search, which marks and unmarks items depending on the match as a form of
  visual feedback.