Children created under first level navigation items do not show up in header navigation.
Say I create a nav item About Us under Home. It works fine. But if I create Our Mission under About Us it does not appear anywhere on the web page, including the source page. It looks fine on the CMS admin “Site” tab section. It is an approved and active (not a draft) item.
The ./tags/webskin/genericNav.cfm custom tag is commonly used for creating primary nav. It generates a nested, unordered list based on the site tree. What displays in the navigation will depend on the setting for depth attribute. And also your HTML/CSS being used for the nav will need to understand the nested list and render it accordingly.
Multi-Level nav is a standard part of the site tree. The only limitation on the size and depth of the tree is that imposed by the theme/views used to render the content of the tree. The site tree itself can extend to an unlimited depth.
You can use the genericNav custom tag to output a nested list, delimited list or query of of the site tree data. However, its up to the HTML markup in the view to determine how this is shown.
genericNav is used to build primary and secondary navigation – after all its just nested UL/LI elements.