In the app just go to the Nomad Lounge page and there's an option for the walk up list. It may or may not be active.
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ETA: When I tried this way it would tell me it was full, but I knew that couldn't be true because I had been on it literally right when the lounge opened. That's what I meant by "not active", not that the button wasn't there or didn't work. I think they hadn't actually opened the online list yet, probably because they had to process the line at the lounge first.