While any Customs can be added to hobbyDB as we asked the PPG community if they wanted to see Custom POPs as PPG only shows products made by Funko (plus the PPG Shirts and one PPG Custom we did).
The answer was clear with 75% of the members who voted saying they did not want to see Customs.
So No for now. But if PPG members want to add a custom to their collection they can find them on hobbyDB here POP! Customs. Adding them to their collections on hobbyDB will then also show them in the PPG Collection and Showcase (usernames and passwords are the same for hobbyDB and PPG).