I have 6 libraries that are shared with various family members. But is there a log of what each user has watched of mine?
Try installing Tautulli (formerly PlexPy).
Not within Plex directly.
But there is a great software for this PlexPy
PlexPy looks great.
I also put together a monitoring “who is watching” that notifies you in realtime (desktop and/or email). Check it out plex-watcher.