It would be awesome if you had the option under games in collection to have a “sold feature” which would include date of sale, how much sold for, quantity sold, platform sold on (eBay, OfferUp, Mercado, etc)

YES PLEASE!!!! Helps so much when tracking a collection. 

Yes, there should be an option in the collection tractor to mark an item as "Sold" if I sold an item in my collection to a friend, TCG shop, or convention. It will make tracking my collection's P&L much more accurate.