I just started creating some video playlists for tutorial videos. When I click on the playlist, it shows the list of videos. It would be nice if the list showed which videos have been watched and which haven't. Maybe you could add another column or the little orange dot. I attached a screenshot.
You can also create a smart playlist from the top level library view and use the 'unwatched' filter. That way the playlist will only ever have unwatched tutorials.
To me this is also a biggie. In fact it is the main reason why I use an AppleTV as my “main entertainment” system in my homecinema instead of one of my nVidia Shields. Because in Plex on AppleTV the playlist DOES show the unwatched indicator (little orange triangle) and I just can’t stand Plex Android without it (I have lots & lots of playlists). In fact, the whole playlist UI looks WAY better on Plex tvOS than on Plex Android. I just don’t get it why it’s so different …