It’s been 10 years :-)… Plex must have good reasons not to do this. However there is something not logical in this whole managed users thing. They are not plex users, the way I see this. Just some kind of “sub-users” under my own account. When I look at this this way it seems completely feasible that those “users” can access a shared library. Why not? It is “me”, not some other plex user I added. My use case (parental control over shared library) is not refuted with the arguments given before. Plex can call it any other way. Maybe they can revisit this feature and allow access to shared library for up to 2 managed home users that are not real plex accounts. I really need this.
—edit
I don’t want to create a real plex account for my children and ask my friend to share his library with them and then manage those accounts by myself. I know this is how people have worked around this but it looks like everything is there to make this happen without extra work. It would be ok for me if those “managed accounts” became “managed devices”. My account - different restrictions per device. HTH