public final ObservableList<MenuItem> getItems() {
    return getWorkbench().getNavigationDrawerItems();
  }
Defines the showing behaviour of the {@link MenuItem}s when hovering over them.
The default value is set to ALWAYS.
ALWAYS:    Triggers whenever the mouse hovers over a {@link MenuItem}
SOMETIMES: Requires one initial click on a {@link MenuItem} to open.
           After that, hovering over other Items shows their submenus automatically
NEVER:     No hover behaviour on the {@link MenuItem}s
@defaultValue Priority.ALWAYS
@return the property of the menu hover behavior
workbenchfx-core/src/main/java/com/dlsc/workbenchfx/view/controls/NavigationDrawer.java