code: protected void addSubmenu(CmsChoiceMenuEntryWidget entryWidget) {
  
          CmsChoiceMenuEntryBean menuEntry = entryWidget.getEntryBean();
          AsyncCallback<CmsChoiceMenuEntryBean> selectHandler = entryWidget.getSelectHandler();
          CmsAttributeChoiceWidget choiceWidget = entryWidget.getAttributeChoiceWidget();
          CmsChoiceSubmenu submenu = new CmsChoiceSubmenu(menuEntry);
          submenu.positionDeferred(entryWidget);
          choiceWidget.getSubmenuPanel().add(submenu);
          m_submenus.add(submenu);
          for (CmsChoiceMenuEntryBean subEntry : menuEntry.getChildren()) {
              submenu.addChoice(
                  new CmsChoiceMenuEntryWidget(
                      m_widgetService.getAttributeLabel(subEntry.getPathComponent()),
                      m_widgetService.getAttributeHelp(subEntry.getPathComponent()),
                      subEntry,
                      selectHandler,
                      choiceWidget,
                      submenu));
          }
      }
docs: Adds a new submenu.<p>
  
  @param entryWidget the entry widget whose children should be added to the submenu