There are a couple ways to preheat, and never step outside into the cold. As mentioned before, use the app to start those functions just before leaving. For my regular daily preheat, I set the timers that are built into the car's electronics to preheat and to time the charging cycle. If I misjudge the departure schedule, use the app as a backup. For my own leaf, it's plugged into L2 charging at home so that's a plus for maximizing range in the cold.
And yep, it's very effective a clearing the glass, and preheating other comfort stuff like the heated seats & steering wheel.