I'm building a custom WordPress theme (not a child theme), and I'm using Bootstrap to "bake in" a responsive menu in the navbar menu.

If you are familiar with coding WordPress, beyond linking to the Bootstrap / jQuery / Popper files, you need a custom "walker" to convert WordPress menus to Bootstrap menus.

So far, so good. Except...

Can't seem to figure out how to get more than two levels (main and secondary), for example this structure:

Home -> Page One -> Page Two -> Page Three

So at the Home page level, the menu should drop down showing Page One with a child Page Two that drops down when you mouse on the Page One menu item.

This is all standard for multi-level nave menus, but all the Bootstrap menu walkers I can find only handle one level below home.

I'm using Bootstrap 4 and the bd4navwalker from github.

Any suggestions?