Sonnet vias can be used to connect metal on any level in a circuit to metal on any other level. They are commonly used to model vias to ground, connections to airbridges, and can even be used to approximate wirebonds.
Sonnet vias use a uniform distribution of current along their height and thus are not intended to be used to model electrically long vertical structures. Therefore, the height of the via should be a small fraction of a wavelength. If you need to make a connection through an electrically thick dielectric, you may need to divide the dielectric into multiple layers to achieve an accurate analysis.