private void setupListeners() {
    toolbarControlsLeft.addListener((InvalidationListener) change ->
        toolbarControlLeftBox.getChildren().setAll(toolbarControlsLeft));
    toolbarControlsRight.addListener((InvalidationListener) change ->
        toolbarControlRightBox.getChildren().setAll(toolbarControlsRight));
  }
Creates an empty {@link ToolbarControl} object and fully initializes it.
workbenchfx-core/src/main/java/com/dlsc/workbenchfx/view/controls/ToolbarControl.java