I can't seem to get this little widget to work. I think you have to actually use the maps navigation, while being connected to the vehicle either via bluetooth or carplay and then once you arrive, it'll remember your parked location.
Its the only thing i haven't actually tried but it is what i've taken by some of the articles I've found online.
Today i drove to work, connected to bluetooth. Parked but the location was never saved or remembered. I didn't use navigation for this ride. Also i do have my home and work address saved under my contact so not sure if this would interfere with the parked car location.