The Saturable Core and Hysteric Core components are actually implemented using the Variable Magnetic Permeance component. You can look under the mask of these two blocks to see how they works. The control signal must provide the values of P(t) (permeance), dP(t)/dt (permeance rate of change) and Phi (flux) as a three element vector.

There are a handful of demo models that then use the non-linear core components. You can find them by filtering the demos to the "Magnetics" category.

One last tip is that for static magnetic components like transformer or inductor, the second port “dP(t)/dt” is not needed (set to zero). However when the permenace is used to model a variable air gap, e.g. for a electrical machine, the second term should be explicitly calculated as the time derivative of the permeance value.