I am not talking about Airport Walkers, I am talking about Pax walking the Jetway.
And what's stops you from placing Airport Walkers inside a jetway ?
However, if the *reason* for doing so was "just" to measure the jetway height to add it to a custom profile while creating one, you don't really need passengers for that, the manual suggests using a temporary Pax Waypoint just as a measuring stick, so you just raised it and read the height, without having to wait for passengers, and a recent update added a vertical ruler to the Pax waypoint market, to make it even easier to see the height.