I played some more with the LED DRLs and have it all sorted now. Would be worth adding this to the VCDS Sticky.
If you want the DRL to dim when indicating, make sure:
(6)-Leuchte2SL VLB10-Dimmwert AB 2 and (6)-Leuchte3SL VRB21-Dimmwert AB 3) is 100. 127 causes it to stay bright. There is no difference between 100 and 127 in light output.
Same for the CD Channel brightness. Default is 26, but I like mine at 100. Just don't use 127.
Then simply set:
(12)-Leuchte2SL VLB10-Lichtfunktion E 2 = Blinken links aktiv (beide Phasen)
(12)-Leuchte3SL VRB21-Lichtfunktion E 3 = Blinken rechts aktiv (beide Phasen)
(14)-Leuchte3SL VRB21-Dimmwert EF 3 = 26
(14)-Leuchte2SL VLB10-Dimmwert EF 2 = 26
(15)-Leuchte2SL VLB10-Dimming Direction EF 2 = minimize
(15)-Leuchte3SL VRB21-Dimming Direction EF 3 = minimize
https://youtu.be/m0R_FJjIPjQ