Easy way to switch from erg to trainer resistance and back to erg?

I’d like to easily switch from erg to resistance and back to erg I sometimes start workout with Xert controlling my Wahoo Kickr using Samsung Android. Xert is setting power level in erg mode. In the middle I want to switch to normal trainer resistance so i can go either above or below target power. Later I want to switch back to erg. For example, I chose CX 2x2. I did the first set of intervals in erg mode and then switched to resistance by going to activity screen and changing the resistance to 30%. I was able to exceed the target power for the second set. I tried to go back to erg in the 3rd by using the workout screen and changing the target power, but no luck. It seems that I can leave erg mode, but I can’t switch back to Xert controlling power. I also noticed that the target power in the fit file stopped matching the workout once I switched to resistance.