Where is the 'submenu' coming from in Photographer skeleton?

I've looked in these threads and done full-text searches of my installation and can't figure out the source or the modification strategy for the sixth menu (right-most) in the photographer skeleton - "submenu.' Any pointers would be appreciated. Thanks - Andrew

It appears to be defined in this file: https://github.com/getgrav/grav-skeleton-photographer-site/blob/develop/config/site.yaml

So it is. Guess I need a new full-text searcher. Thanks for your help.