Isolated three level pwm LTSPICE
With a bv source you can use math equations, so just for simulations take if you want to stimulate a combination of signals you could do something like this:

bv=V(pwm)*V(gatesignal)+V(whatever)


Where pwm, gatesignal and whatever are net names. If you want to reference a current you can use I(netname)

If you want to physically realize this system you'll have to do it with analog multipliers and summing op amps