Power curve used in Zwift with classic Tacx trainer

Hey…I’m launching again this question bcs I have doubts how the different power curves are used by Zwift.

I understand, from previous entries, that my tacx booster (dumb trainer) with sensors (speed&cadence) should work using z-power or virtual power, and the known power curve from this tacx trainer. But with this trainer you can shift manually the resistance between 10 different levels, so you have 10 different power curves.

how this is implemented into Zwift? could I change the resistance on the trainer and inform zwift somehow (this way I can use the complete power range of the trainer) or should I fix a certain resistance level and then the curve used is always the same?

in other words, how Zwift knows the resistance level (and thus the power curve) I have selected on my tacx trainer?

thanks in advance for your help and keep riding!!

I see you have a duplicate post here so i am going to close this one so we keep all the answers in one place.