Sure this works but the way it works with Movies is far superior. I hold out hope that this will change. At the very least, it could auto-detect the title that appears after the fake episode number!
Some of my favorite shows have extras that are actually worth keeping around to watch again.
The Season 00 or episode 100 workaround is one ■■■■■■ workaround. Just shows all your content scattered in a mess under one season. All that is needed is a folder for these extras (but not “extras” because that’s an IGNORE catch for PLEX??? why I don’t know); but some named folder (maybe DVD EXTRAS for example) under each SEASON folder for organization sake that you could dump the files in.
Seinfeld/
…Season 01/
…DVD Extras/
…Seinfeld - DVDXtra - The Stake Out - Inside Look
…Seinfeld - DVDXtra - Not That There’s Anything Wrong With That (Bloopers)
Plex would then simply show the contents of that folder under each season in a section underneath and marked/separated off from the actual episodes; maybe with a line or heading saying DVD Extras under the main season episodes. TVDB is totally useless for these things, so you would have to manually edit the metadata, which isn’t hard.