I can link to my new bike's eTap, but i can't select the correct gearing in the Sensor Details. I tried the 9.10 release and it did have my 12 speed cassette in the list, however, it would only display 11 gears. I just loaded 9.26 and it does not show any 12 speed cassettes and does not have more than 11 gears available as a Custom configuration.
I do see in the forum that this was being worked on 2 years ago for Edge 820. I don't see any resolution on it.