I also came here in hopes there was a way to set up something similar, my problem is that my library contains movies in different languages. I'd love to separate foreign movies from domestic, and maybe even animated movies from regular ones.
As i was reading through the thread, (i skimmed the end of it, if i missed someone posting the same thing i apologize for the duplicate) i had an idea: why not just add a single field to the general library table that would allow us to create subsets from the general library, and let us set the field with a drop list in a movie info or from sub-menu in the context menu when you right-click on a movie.
A new table in the myvideos60 database called subsets or something, with two fields - integer for index number, and text for the name of the subset, it'd contain user generated list of all the movie categories. Zero value index could be reserved for any movie that doesn't belong to any subset, anything greater.
Then in movieview table add another integer variable that would just simply hold the index number of the subset.
Now when i click on movies, if there any subsets defined, i would see list of the subsets instead of long line of movies all mixed together. once clicking on subset, i would see only movies belonging to that subset.
It could be customized further by expanding the subset table with path variable for fan art or thumbnail representing the subset, along with the name.
Someone might object that we already have this functionality with movie sets, while it partially does what people are asking for, there is no easy (read: quick) way to set it, i like the movie sets feature as is, and I'd hate to lose it just so i can separate my library by language.
This might even be doable with an add-on instead of it being built into the XBMC itself.
I'm sure there are people who could refine this further to make it work if not for everyone, then for vast majority