Without thinking through all the implications, I think the View Extras functionality would work better if it only showed files that began with the same name.
So a movie such as "The Seven Heros.mkv" (or AVI, MP4, JTV, etc.) in a folder full of movies, would only show files named "The Seven Heros*.*"
i.e.
"The Seven Heros_Poster.jpg"
"The Seven Heros_backstory.pdf"
"The Seven Heros_trailer.mp4"
"The Seven Heros_trailer2.avi"
etc.
I think that would fix some of the earlier problems mentioned, but would make some special cases for audio with "folder.jpg" files and such. You could also just specify that MC should search the folder and all subfolders of the folder the media file is in, probably just one level down for speed reasons, and you wouldn't need all the special case subfolder searching, such as "Extras", "Album Artworks", "Scans", "Artwork", etc. Then anybody could add any subfolder they wished to, and as long as the Extra
files started with the name of the media, they would be shown via the "View Extras" menu.
Then I would like to be able to invoke a Trailer (or two) from within the information display for a movie in Theatre View, either via the top menu, or preferably via clicking OK on an info field. Trailers would be imported into MC like other videos, and I would exclude them from the Movie view, but would also create a view of just Trailers, to browse through, or just as a "quick fix" of entertainment. Some trailers are very entertaining, and I could imagine watching a sequence of, say, Marvel Trailers instead of watching a whole movie.
I have too many directories with multiple movies in them for View Extras to be useful at the moment, home movies being a specific example, but a bunch of others as well. I am cleaning them all up and moving each video to its own directory progressively, but that is going to take some time. Plus I probably won't do that for home movies. They sit in a directory based on category.
Of course if the above was implemented, then the RM&CF function would have to, optionally, rename all Extras files, at least the first part of them. It is a challenge, isn't it.