Don23

I'm sure most of you know this, but adjusting the RD on a DI2 bike is amazingly simple...making dialing in the RD for trainer and then for your rear wheel easy enough to do each time you switch. Press and hold the button until the light goes red putting it into program mode and use your right shift levers to adjust RD left or right until you have a quiet drive train, hit the button again and you're all set.

The video I used: https://youtu.be/P5EEd7eRUFY

PoorInRichfield

I take it you are finding yourself having to adjust Di2 each time you transition between your trainer and off?

I just entered into the world of Di2 this winter and am waiting for a thru-axle adapter to arrive for my trainer so I can put my new bike on it. I'm lazy and I switch between indoor training and outdoor riding quite often, so I'm looking for the "least amount of work" solution to this rear derailleur alignment issue. My plan so far is to have the same cassette on my trainer (Wahoo Kickr) as I do on my bike's rear wheel. If I find that shifting isn't exact between the two, I'm hoping I can use some thin spacer washers on the trainer to get perfect alignment of the cassette. Of course, using spacers can only move the cassette away from the trainer, so if the issue is that the cassette is already too far from the trainer, then I have a different problem to solve!

Don23

I would say the process I outlined above would be easier