If the subfolders for each movie are correctly named & organized, then you may not need to move things out of the library then back into the library (less shuffling).
Test with two or three movies.
- In one of the movie folders add the desired subfolders for extras (interviews, trailers, etc.).
- Move the extras into the desired folder.
- Scan the library and empty trash
- Refresh the metadata for the movie.
That should pick up the extras and display them properly.
If it works, then you can organize things for all the movies, scan, empty trash, and then refresh metadata for the entire library. Basically, do the scan/empty trash/refresh metadata on the entire library instead of movie by movie (easier & faster than movie by movie).
If that does not work, then Plex Dance the movie (move the entire movie folder including extras). That will clear out bad information from the Plex database.
Also consider simplifying how you name the movie folders and files. It works, but that is a lot to add and track. It will make maintaining the server easier with shorter names.
A lot of the info is redundant.
- 4K, 2160p, and UHD are essentially the same thing.
- HDR & Dolby Vision movies from Blu-ray discs are HEVC 10-bit video (some streaming services have started using AV1).
- All 4K discs are Blu-ray. Use “BD” if you want to differentiate a Blu-ray rip from a different source (dvd, download, etc.).
For example, instead of:
/movies
../Red Dragon (2002) [Kino Lorber Studio Classics + BluRay Extras) 4K 2160p BluRay x 265 HEVC 10bit HDR AAC 6 Ch (2002)(2023)]
..../Red Dragon (2002) [4K 2160p BluRay x 265 HEVC 10bit HDR AAC 6 Ch].mkv.mkv
Consider something like:
/movies
../Red Dragon (2002)
..../Red Dragon (2002) [2160p.HDR.BD.AAC 6 Ch].mkv
It is your server and up to you about how much extra stuff to add to a folder/file name. Just remember that the more time you spend naming & organizing the less time you have for actually watching and enjoying. 
