I have an inelegant solution for this (inelegant because I developed it before I got deeper into expression language; and now I'm too busy to go back and fix it, though I probably will at some point; and I'm open to better suggestions here
). I basically use [Grouping] and tag each mkv either "film" for the feature or even a short film (lots of Criterion Collection releases, for example, include shorts by the filmmakers) or "Extras" if I'm keeping an interview or a "behind the scenes" or whatever. I also use [Part] (don't remember if this is a standard field or one I created) so that I can distinguish different cuts of a film (just mkved the "Salt" blu-ray, for example, and it contains three cuts: theatrical, extended, and director's), parts of a TV series, etc. Then in my view scheme, I use a simple expression to distinguish between film (and different cuts, if there are such) and extras. It gets a little cumbersome when I stream to my DLNA device (Mede8er X3D600), as I have to click through too many screens when I use UPNP, but it does work.