Here is how to adjust the height of the liftgate:
I have a SEL and here is how it works on an SEL. I would assume it is the same.
Turn the Car on --> Set up --> Vehicle --> Doors - - now scroll down to the bottom of the door choices. You'll see Power Lift Gate. There are 3 preset levels of opening and 1 custom height opening. I set the custom height. I opened the garage door, then the lift gate. I let the liftgate open all of the way, pulled and pushed the liftgate to the desired height and then you press and hold the close door button (the button on the liftgate that you use to close the liftgate) for 3 + seconds. That is all there is to do.