I have a few shows like the Daily Show I'll sometimes watch the monologue but not the full episode.
Plex has a setting to "Keep unwatched episodes" which will delete never-watched episodes, and another to "delete X days after viewing" for fully-watched episodes. But if an episode is partially watched, neither applies and it just sits there.
This seems like a weird oversight and I am wondering if there's a setting I'm missing. I can't be the first person who wants "delete 7 days after adding regardless of anything else"
You could manually mark the episode as watched after watching the monologue.
But the question was if this could be done not manually.
I don't think so.
There is an option for the % of the episode you need to watch for it to be considered "watched", but the lowest it goes is to 70%. Maybe you could edit the config to set it to a lower value. But of course that would mess up shows you actually want to partially watch and resume later.