I'm confused... what about the parking brake requires starting the car?

Just pull the release handle in the car.

Or are you talking about getting the transmission out of Park? The W123 doesn't lock the trans into park with the ignition off, you can just shift normally with the key off.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.