Navigate backwards in the menu tree structure. For a PopupMenu, it just closes it. Otherwise, it will bubble up the tree till it gets to a Menu, where it will cause the previous Menu in the MenuBar to be selected.
Navigate forwards in the menu tree structure. For a SubMenu, this will open the open. For other menu items, it will bubble up the tree till it gets to a Menu, where it will cause the next Menu in the MenuBar to be selected.