I'm not sure how this pseudo-solution would work for the Album Covers view, but in my Soundtrack view, I use <Sort Album> to combine. For example, I have both the soundtrack and score to "Back to the Future," but they both are under a single "Back to the Future" slot in the <Sort Album>-sorted Thumbnail Browser.
It's less about combining them into a single list and more about being able to alternate between different versions within a single album, IMO. Once you're combining multiple large albums together, at least in my case, they become overwhelmingly long. Using my above example, my four Pirates of the Caribbean: On Stranger Tides albums are 27 tracks (OST), 106 tracks (demos), 14 tracks (fan edit), and 92 tracks (complete) -- a 239 track list if combined. As with anything though, we all have our own ways of listening / collecting, so this'd really only work if it were a toggleable feature
I do have a few separate albums combined into a single "album" as I sort my core playlist by folders, so that's actually fairly easy enough to achieve with the Album Covers view. It can be a bit strange with the music explorer and can throw off library stats but otherwise it works ok. I'm sure there's an easier way of doing it but I'm a simple person haha