As talked about on the Tiki developers mailing list, it would be good to support alternatives to the standard Bootstrap navbar. There are quite a few examples of offcanvas menus, etc. Some are used in all display sizes, and some are used only in small screens to replace the standard horizontal navbar.
Here are some scripts/libraries and docs (not checked yet regarding license and other details):
Also, related ideas: - Bootstrap 4 Mega Dropdown Menu Navbar -