How to have mix "movies" + "shows" in one folder

[Duvel]

Generally speaking, we highly recommend NOT making a mixed library.  The file name parser can't handle both movies and shows.  A lot of people have their library setup this way, including me.

Anime shows
Anime movies
Movies
TV shows

This way we can use anime centric metadata sources, like AniDB, on the Anime libraries and then TMDB/TVDB on everything else.

Over the last 3 years I have read this several times from Jellyfin admins, and this stance is not realistic. Mixed contain should be a thing and is not avoidable in many situations.
I think you are all missing the point, probably because you dont watch documentaries, and also because you have a english-speaking-only and US TV broadcasting  approach of things.

First you have to make a documentary library mixed because there are one-shot documentaries and multi episode documentaries. Example : Fahrenheit Eleven is a one-shot, Cosmos is multi episode. There's no point to display Farenheint as a serie, it should be displayed as a movie.There's no point either to put it in a "Movie" library, because it is a documentary. 
And there's no point in splitting your documentaries in 2 libraries that would be either Oneshots or Episode based. Because a library should be functional and not technical.

Secondly users can have a lot of TV shows that are not a "serie", but rather "local contain" created by national state-sponsored broadcasters that are usually the most watched in a country, at least  in Europe. Like BBC, France Television, Rai (Italy), TVE(Spain), RTBF and VRT (Belgium FR and Belgium NL), etc...  You may have one-shot shows or episode shows. And it can be anything: political debate, Investigations, Nature doc, Humor/family show, Theatre play, etc... And it is completely logical for some users that those are in the same library.

The mixed libraries works more or less with Jellyfin once you have understood how to excatly structure the subfolders, so the parser can switch over oneshot or episode based contain... it took me a while to understand this. So I personally dont have much issues with how it works at the moment, although there's room for improvement.

But each time I read an admin writing what you wrote I am fearing that one day you will stop supporting the Mixed contain or at least not improve it anymore, because you dont understand how important it is.... and this would be bad for a part of the user base.

I mean, instead of discouraging users to have Mixed contain library, you should just do the exact opposite : improving the Mixed contain parsing and display, and encourage users to use it in some situations because it just work well

IMO the first thing to modify on your end, would be to let the admin define if something in a mixed library is oneshot or episode based so the parser knows exactly where it should look for metadata and the GUI how it should display the contain.