Firstly today is the first day I have used the tool, so I am not an expert.
In answer to your question from what I have seen so far today you do a scan.
select module 9 Electrical something or other.
Then take the option - Adaption (sorry I know you know this bit but its easier for me to do long hand)
Then you have a number of options select Select - Leuchte17TFL R R SR BLK BLK SRB3TFL light KC3
(which I cant see on my 2014
Cupra I have something like Leuchte17TFL BLK BLK SRB3TFL)
Then you will have a drop down list, looks like you then select Lichtfunktion A16 and change the value to 127
Once done this will take you back to the drop down menu and you then select etc etc.
I am going to go back now and see if I can work out what I have done wrong,
Managed to get a few changes but not this one.
Keep us updated please and hope this helps.