You can actually hit just about any HVAC button and turn it on (except defroster, lower air flow, seat heating or menu) when the car's in standby state.
I just hit the fan button when I'm waiting in the car and want it to stay warm. It shuts off when I open the door and lock it though. But it works great if I'm picking somebody up or getting gas (we can't pump our own in nj and that's fine with me
)
Or:
Car>settings>climate control>pre-ventilation>activate now.
Or:
You can use your remote control or the app and remote start to get it warm.
Check out the drive guide under "stationary climate control"