final void addOverlay(Region overlay, GlassPane glassPane) {
    LOGGER.trace("addOverlay");
    overlay.setVisible(false);
    getChildren().addAll(glassPane, overlay);
    // make glass pane hide if overlay is not showing
    overlay.visibleProperty().addListener(observable -> glassPane.setHide(!overlay.isVisible()));
  }
Stacks the {@code overlay} on top of the current view, together with its {@code glassPane} in
the background and makes the {@code glassPane} hide, whenever the overlay is hidden.

@param overlay   to be stacked on top of the view
@param glassPane to be added in the background of the {@code overlay}
workbenchfx-core/src/main/java/com/dlsc/workbenchfx/view/WorkbenchView.java