Much like the blue markers for unwatched, partially watched and watched videos, it would be great to have a watch marker for a whole folder / directory. This would be ideal for TV shows that don’t necessarily require you watch in sequence or order of release, such as education, science or doc series, but are still ideal to sort into seasons. Ideally, the moment you watch one video/episode, the folder watch marker would change to a partial one too.
It would also be an easy way to mark a whole season/collection as watched or not.