No. As you cannot move the file(s) inside Plex, it’ll be like a new file to that new library of yours.
If both libraries use the same “agent” to match the show / movie, Plex should however remember the view state (potentially your individual ratings).
Are those shows/movies getting in the way in your main/original library?
If so… have you considered simply adding them all to an “Archive” collection?
It’s just a regular collection that you configure to hide its items. While sorting your library by a movie/show title the items associated to that collection will not show - only a collection entry which you could name „Archive“.
It’s nothing fancy but it’ll help keeping the library itself tidy (assuming that’s what you’re aiming for)
What is the main reason for wanting to have separate libraries?
Plex has a “played” indicator on every episode and movie already.
Why do you have to move the item to a different library, once you have seen it?
And keep in mind that Plex is a multi-user solution. This whole watched/unwatched library paradigm breaks down into uselessness when more than one user is involved.
I am currently a SageTV user. What I like about the interface, is that I can mark a show or series as archived. It then does not show up in my main display. I usually have 30-40 current shows in my display and there are 70+ shows in the archive. The default for SageTV is the list mode, which is not available on PLEX apps.
What I am trying to achieve clean main display. Using the watched indicator will not work, because there are shows in the archive that have not been watched.
I am just looking for the best way to implement this.