So, this is my experience with the secret Harry Potter door. I am on Floor 5. I was told to go to Level 4 (Level 5 is smaller) and go to the elevator nearest the highest room number. Then to to Level - 4. That’s negative 4.

As in the photo above, the sign says Jeffery Street. And there IS a white intercom box. And the door is no longer white. Nice little entrance area, no access to anything but an elevator.

I have not yet tried to contact the desk via said box but a workman guy said I could.

Only issue is, upon entering Waverly, the Handicapped Lift is currently out of order. So you have to go down around 12 steps to reach an escalator. Still very much quicker than walking up North Bridge as sidewalks on one side are closed. Then you have to walk a block to the Princes Street Elevator or the Waverly steps/escalators (one of which is also out of order.

Here is the door. You would need a key card to operate the elevator. I think. Will confirm.