I’ve just had to setup my server again from scratch and I didn’t realise how many entries I had to update manually over the years because some documentaries are categorised as movies. What I don’t want to have to do is split my documentaries section in half, I want to be able to find a match whether someone has categorised it as a movie or tv.
Plex cannot do that. Your best shot is to go with 2 documentary libraries (1 for movie and 1 for tv-show based documentaries) – unless you want to use the “personal media show” for that one, feeding all the applicable metadata into the file itself.
Personally I’d go with the 2 documentary libraries. If it helps to make them more “translucent” you could assign shows/movies to a same-named collection to link them (e.g. one documentary collection for sports / football / …)