If you sign out and sign back in, Plexamp will auto create the smart playlists (Recently Play, etc.). But this happens before you have a chance to switch users. This causes a problem for managed users. I have yet to find a way to create these system smart playlists for managed users.
Qué?
Please explain what is missing for your managed users.
Scenario 1:
I have no playlists tied to my account. I login as a home user (test@test.com) into Plexamp. Plexamp will autoocreate a bunch of useful smart playlists.
Scenario 2:
I create a managed user (bob). He has no playlists. I first have to log into Plexamp with test@test.com. I then switch to user bob. Plexamp will not autocreate the smart playlists.
These smart playlists were simply intended as a hint to create your own smart playlists (which might even fit your personal use pattern better).
They are currently only created for the main user, but not its managed users.