You (and anyone else on the forum) are always welcome to tap me for questions, especially if it's a how-to question about a Club service. Questions help me refine the various services available to the collector community.
I agree that the Marketplace is geared towards selling individual pieces that are listed in the Master List. It's not made to sell anything not on the Master List, e.g., collections. I have toyed with the idea of creating a marketplace for items that fall outside the Master List, but it seems other people are setting up Facebook groups to sell such items, so I have put the creation of such a marketplace on the back burner. Frankly, I'm relieved: It would entail a lot of work.
Facebook is actually poorly suited for selling stuff, but if people feel it's adequate, then I'm glad people have somewhere to go. The Club Forum used to have a Marketplace bulletin board, which could accommodate collections and such, and it was better organized than Facebook, but so few people used it that I discontinued it when the Marketplace went public. I'd be willing to resurrect it if there were sufficient interest.