Multi-level navigation and easy menu definition

[mvlcek]

Does anyone have an idea how to display a menu tree containing slugs of defined page, where slugs also have nested pages, but slugs on lowest levels shouldn't be opened until visitor clicks on their parents.

Isn't this the standard behaviour?
If you click on a page it is shown with its siblings and children (and parents and their siblings). If you click on a child, it is shown along with its siblings and children.

To not show the first level, you have to use <?php get_i18n_navigation(return_page_slug(),1,99) ?>.