Originally Posted by Sierra_rider

What I do, is I'll load my custom workout/interval session onto my Garmin head unit, but I don't let it control the trainer. I'll then ride a virtual climb and self-pace my intervals without using ERG mode. You basically just connect the trainer as a power meter to the head unit(or in my case, I just use the power meter on my bike.)

The downsides are that you have to pay attention to your power output and it can be affected by the virtual gradient. The positives are that it's a more realistic experience and that it's much more mentally engaging than just plodding along on ERG mode.