If you go to the player and do a collection summary. then add/update then the pull downs if you click on Don't Have it will show you all of the cards of that player that you have listed as "Wants" (in pink) and cards (no color) you have not listed any other place.
There is a new feature request that would make changes to the Don't Have list that would only show cards you have not put in any other place (New cards). If the new feature is done all you would have to do is look at this area and see any new cards added to this player that you have not seen and decided on what you want to list it as.
New Feature Tracker | Trading Card Database (tcdb.com)
