I've completed the first steps of the project successfully. I'm just waiting on the tail lamp to arrive to finish up.
I have a 2018 SE built in 11/2017, after they stopped installing front fog lights on all S and SE models.
First check was to see if there was a front fog light trigger wire in my headlight switch harness (pin 5), and there was. That saved running the trigger wire from the switch to the BCM.
I then swapped out my stock NAR headlight switch to a euro one. The part I got off eBay DE is 5G0941431BD. It has stops for both front and rear fogs. To be clean, I should have gotten the one for rear fogs only (5G0941431BE - no front, rear fog stop only) but I got this one just in case I want to add front fogs at some point.
I followed the MK7 Golf (MQB) coding instructions for the BCM using VCDS:
Select: 09 - Cent. Elect
Select: Security Access -16
Enter the Access Code: 31347, then “Do it!”
Select: Adaptation - 10
Select: New Value "Yes", then click “Do it!” (This tells the BCM that a light switch with rear fog function is installed)
Search:Leuchte28RFL LC11-Lichtfunktion A28
Select: New Value "Nebelschlusslicht wenn kein Anhaenger gesteckt", then click “Do it!” (This tells the BCM that the vehicle is to use a rear fog in that lamp position, formerly the reverse light)
The light on the dash came on (yay)
And here's how it looked at the rear (obviously not red - yet)
Everything has gone to plan so far. The last step is to install the inner-left tail lamp which has the rear fog light (lights red) instead of the reverse light (lights white). I got it off eBay DE and it should arrive in a week or so. The part number I bought is 5NA945093F.
I may have to move a PIN on the lamp harness connector, depending on whether or not the new lamp uses the same A28 light position. Of course I'm hoping for plug and play - fingers crossed - though I could run into issues with the connector shape too.
I'm hoping the lamp color is the same as the others. VW has so many reds (red, dark red, cherry red) that it can be hard to tell until they're held up against the existing lamps.