Hi I was wondering the same thing but then was told if you keep your finger pressed on the remote to unlock the car, then the tailgate window opens... I tried and mystery solved.
just tried that on my 3 door and it does go down when you keep your finger on the unlock button but doesnt seem to close when you hit the lock button. why let you open it then have to get in the car and put the key in the ignition to close it again. i suppose to allow you to put stuff in the boot but would be handy to be able to close it again without having to get in the car.