Modern-Folder Permissions Setting

Hi folks
It is about the role concept at Modern-Folders.
I would like to build my concept so that there is a role that allows to add new (existing) users to a subfolder within a certain folder (but only for this folder).
I’m not sure if this works at all, I couldn’t find anything in the “About Folders” section.

Have you ever tried that and I have an idea how to create the role and where I have to assign it (to the user or to the folder)