Yeah, it's not great. We had to add logging into our custom app to get around this. The only thing you'll see in logs when adding a delegate is the OAuth log entry for Gmail, which doesn't tell you a lot.

As far as I can tell, adding a delegate or forward isn't even logged anywhere, and being able to see what a delegate is doing was added as a feature only a few months ago: https://workspaceupdates.googleblog.com/2022/03/gmail-delega...