first of all let me say I really appreciate your precious explanations that cleared up many points that were obscure to me and the same for your help in general!
Support Team wrote: Sometimes you can create out-of-page menu items to fix specific Urls.
This seems a great idea, however I tried doing a menu of the missing categories and unpublishing it: it does not work. If published, it works. Can I workaround this somehow? Trying various ideas in the meantime...
This is needed to avoid the "/inserimento-articoli/" path that I think should not at all be there anyway, because it's the special-access only submenu for allowing editors to write articles and the plugin is set to only see public stuff, so I still am not sure why this is teasing me
OK, I got it, you explained it greatly already, I just caught it late
I can simply create a completely brand new menu, a module for it in a non-existent position, then add into it a menu voice of type blog category or similar that lists things of the categories that have no (visible )menu. This way I can also personalize similar pages. Brilliant