I don’t believe this is possible but said I’d ask just in case it is …
I had recently re-setup my plex server from scratch, adding libraries etc… and as all media is added as unwatched I then manually set a large amount of media as watched.
If I goto the dashboard and view full history I see all the stuff I manually marked as watched. Is there a way to delete this statistical data, setting my view history to zero but leaving my watched media as is.
the ‘full history’ may always be influenced by the manual watch status, but as time goes on, you can use other history ranges ‘week/month/year’ and those initial watches become less important/relevant.
the more complex answer is, maybe if you know/understand enough about the library database to clear the applicable tables/records.
Assuming it is even possible to do so without corrupting the timeline going forward. (I personally have no idea)
In any case, everyone has to start from somewhere, so whether you bulk edit a bunch to ‘watched’ up front, or you watch them ‘over a period of time’, it more or less comes out all the same.
you might investigate ‘trakt’ which is a website, that plex has a few different ways of interacting/syncing with, that can help ‘track’ your play and collection histories (along with ratings and playlists) outside of plex.