It takes about 10 seconds to lower to entry/exit level and if you open a door before it is completely down, it will cancel and go back up to previous level, aero or normal. It can not be programmed to go down by itself and if it could you would need to wait the 10 or so seconds before opening a door.
You can bush the button before you park and it will lower when you go slow enough before you park and open door if pushed more than 10 seconds prior to opening door.