The way collections work now pretty much covers only a “Add everything available” way of use, but with just a couple of tweaks it could be a lot more versatile.
Personally, I’d love to use it as a quick favorites list for each system. If besides of scanning complete directories you could have access to an “Add to/Remove from collection” from the Quick Menu (similar to how Favorites work on Steam’s ingame overlay), you could easily use it in this and more versatile ways.
What would it take? The entry in the Quick Menu just needs to check if it exists on the list file, add it if it doesn’t or remove if it does, and re sort the list alphabetically.
I hope this sounds good to you. Thanks.