Plex does not support local extras for tv shows.
You can organize those as “specials” or give them high episode numbers inside their season of origin… this will give you the option to manually enter some metadata.
There’s a feature suggestion to allow the addition of local extras for tv-shows (which I’m personally very much hoping will be implemented).
From what I remember there’s also a 3rd party agent that allows to find local extras for tv-shows that match the same schema as local extras for movies. Those will show in some Plex apps but not on all levels (show/season/episode) and not in all apps!
