Are standing lights the same thing as parking lights?
On my '82 300D, the full array of parking lights (one click to the right on the rotary switch) will work only with the ignition switch on.
However, you can turn on one side at a time without the ignition switch using the switch positions to the left. Really freaks people out - they always think you've got bulbs burned out in the car. One click to the left turns on the right side, and the second click over to the left turns on the left side parking lights.
This feature cuts the electrical consumption in half while in most cases providing the necessary safety lighting. I usually fuel the car in the early morning on the way to work while its still dark. I ALWAYS leave on one side of the parking lights while fueling and paying inside. I hope it helps people see the car better when pulling into the station half awake!