Each TLW topnav submenu is composed of a single shared content page, which contains mainly FlexModule components. At the top of each shared content page, there should be a shared content reference to /content/demo/shared/prototypes/tlw-rollovers/topnav-submenu/source/css, which will apply appropriate styling to each submenu in both author and production.
A shared content reference to each TLW topnav submenu should be placed just after the main-include reference on the header config page. The order of each submenu reference is important here; each one will be used in the topnav ordered from left to right. If a submenu reference is not present for any of the menu items, then it will be initialized without a submenu.
Finally, a shared content reference to /content/demo/shared/prototypes/tlw-rollovers/topnav-submenu/source/js should be placed after all of the submenu page references on the header config page. This is responsible for injecting each submenu into the TLW topnav.