Multiple independent menus
If you need multiple independent menus, you can create (empty) dummy root pages and arrange all menu items below either of them, e.g.
menu1 item1-1 item1-2 ... menu2 item2-1 item2-2 ...
Then to display a menu, use the following code (here for menu1):
<ul> <?php $bc = return_i18n_breadcrumbs(return_page_slug()); get_i18n_navigation($bc['url']=='menu1'?return_page_slug():'menu1',1,99); ?> </ul>
Unless you use reasonable names for the dummy pages, you should probably not use the %parent% page in the custom permalink structure.
(If all but one of the menus are rather static, you could also hardcode them into your template instead)