No, there is no indicator because booking doesn’t need occur from the LoungeKey app itself. It simply tells you where the lounges are and the amenities they have. You have to go with your card and swipe it, or in the case of Revolut show them a QR code.
Here’s a screenshot of the LoungeKey app, to show what I mean (this is with N26 Metal membership)
There is literally no way to know if you’ll be accepted into the lounge until you’re there.
On top of that LoungeKey doesn’t guarantee any guests either, which is awkward when I want to take my girlfriend into a lounge only to find out that they’ll only let me in it’s up to the lounge itself. (This has never happened to me)
Luckily most lounges with LoungeKey tend to sell access on the door anyways