Any chance to show the folder structure/hierarchy or a folder navigation bar on the left side of the window?
Show all folders to shared group, but the access to each folder can be restricted by admin.
For example, User A has two shared "Folder A"s. but User A doesn’t know which is from Project 1, which is from project 2. Assume we can show the folder structure, thus user A can directly access "Folder A"s by clicking the folder on the folder navigation bar.
There can be work-arounds, so you could use an external storage with this feature, e.g. SMB or similar where you manage the permissions via SMB so that only certain people have access to Project 1 or 2 and only see those subfolders they have the permission. You can then use this SMB-stuff via external storage plugin. But it won’t be within Nextcloud itself and Nextcloud would index the files seperately for each user even though these are the same files.
Another idea is with file access control (and perhaps tagging): https://nextcloud.com/workflow/
The direct integration into Nextcloud is a big plus. I haven’t used it enough to tell you what is the best way to obtain what you want to do… just play around a bit. Perhaps there is something on the documentation as well (if not we should probably extend it).