Welcome! Tis the season for not wanting to sit in a cold car while it warms up haha. Before I had a remote starter installed I came across the same problem. Probably the safest solution without leaving your car unlocked while it warms up (there is no killswitch if someone gets in and drives away) is to lock it from the outside with the physical key that detaches from the fob, its the same function as if you were inside the car and locked the door. Its an extra step but better than risk someone possible getting in and/or driving away.
If you do decide on a remote starter, you can check out a local reputable shop to get it installed. If you go to a dealer they will subcontract the job out to a local 3rd party shop and charge you more to make up the profit margin between original shop price vs price you pay.