I know the queue option is there for media and things outside of Plex, however I would love to be able (mainly for TV Shows) to add the ability to Favorite a series I have in my library - basically subscribing to that series. I can go to favorites and see the series I've been keeping a track of watching and I can see when there is a new unwatched episode for that series.
While having favorites might be a global option for Plex, please remember that how it is handled might (and should be) different based on each client implementation.
Early 2021 clean-up: duplicate