As a normal user of Nextcloud I would like to see on each folder, who shared it and who has got access. Currently this can only be seen on shared folders themselves, but not on subfolders. This feature would increase the users trust in this file sharing solution.
As second best solution there could be an app for admins, which calculates the authorisations for subfolders and allows reporting.
I know, that file access control rules can make this a bit complicated.
As benchmark I see the Google Drive feature for sharing.