Example resources and the interesting spots
The navigation level is added via the sitemap editor. Open the "Add wizard", choose the tab "Function pages" and drag the navigation level to drop it into your sitemap. Sub-pages are added as normal container pages.
In the sitemap editor, the navigation level is highlighted as a blue folder. Below, you see the sitemap for the example presented here.
If you are offline you can open the sitemap editor from this page and reorder the sub-pages of the navigation level. See what happens if you click on the navigation level again. It should redirect to the first sub-page of the navigation, to which this page is equal.