Has anyone used Mobile Passport.
Returning to JFK, we didn't see a line for it, so we went into Global Entry, as they have been combined before.

We didn't stop at the GE machines, because we weren't sure what to do.
Luckily the guard let us right through, but we didn't learn anything.

I looked it up, and it said there should be a special line---and sometimes it is hidden. We have been using MP for years.

No one got stopped at Passport Control.