I will periodically, audit my database where I compare my collection on the shelf with what I have in the app. What would be nice is if I could filter the collection so that I have a subset, like all physical titles for a given platform then put the app in inventory mode. Then I could go through each game and tick it in the app and then it would allow me to see if anything is missing (which has happened) or on the flip side, something I forgot to add (which happens more frequently).
Something like this has been on the ideas list since the Windows version. It might happen at some point. We had a couple of requests for it over the years.