There isn't any kind of "dry run" or "phantom" mode, where requests are not actually blocked, but appear marked in the log UI as "would be blocked". This is super important because I want to see all the things my home network is doing that would be blocked before I actually hit the big red button. I want to fix up the allow/denylist before going live.
It's also not possible (or not clear) how to have different behavior for different clients. For my "smart tv" which I begrudgingly have to allow on my network occasionally for software updates, I want to treat it with the strictest possible list. But for my phone, I don't want that same list. There's a concept of "groups" so perhaps this is user error on my part, but the UI does not make this clear.