I fear you may struggle with multiple versions of the same episode as Plex will stack them, hence those that have numbers in the top left.
(You can select a version when starting playback, but nothing useful is displayed in the selection window, so it is hard to know which is which)
I am not familiar with that plugin, and it may do want you want but I don’t know. Plugins are not really supported anymore, although at least some metadata agents still work. Just not sure how you use that one.
For things that are not episodes, you could put those in a specials folder.
If they are not in the TVDB as specials, then you should number them higher than those listed in the TVDB. (I think there are about 60 specials so far) So maybe number yours from 100 e.g.
Doctor Who - s00e100 - My Custom Special 1.ext
Doctor Who - s00e101 - My Custom Special 2.ext
You would need to manually edit your custom specials, as they will just display as Episode 100 etc
There is also a current issue with Plex and the TVDB, so if you want metadata, you will need to fix match for the show and enter the TVDB ID (76107) (see my post here)
