As per leelynds response:
You can already do that. Plex will recognize local extras for all tv-show tiers… shows, seasons and episodes.
The only downside is that not all apps will display extras on all those levels. There’s an existing feature suggestion asking to close this gap. So unless you’re looking for something completely different, I suggest you comment/vote I. That thread in order to avoid distracting/dispersing votes.
