I'm working building my customization on the quickstart for J5.
I created my home page and I duplicate the template fromthe corporate layout to apply css customization only on some pages.
Today I created some new menu items, and to optimize space into the navigation bar, I nested the original joomlart menu items under my home menu item.
As soon I nest the Explore menu items, any other menu items disappear except the home. As soon I put back the explore menu item into the navigation bar, all menu items became visible