@Wooter : So, your Leuchte-set doesn't contain a specific command to illuminate the DRLs.
This means (I think) that the low-beam behavior on your car is enabled by
Außenlicht_Front-Fahrlicht bei Tag , which is a channel in the central electrics module
Maybe try the procedure in my pics below (select "Normal"). Based on your answer to my question about what happens when the rotary light switch is in the 0 position - I suspect that the channel setting on your car is the last option in the 2nd picture below?
Don