I'm not sure that I understand. Solar is supplying power to the battery. I am assuming that your transfer switch will supply power to the battery from another source. It is not necessary to disconnect the solar from the battery when you add another source to power the battery. My solar is ALWAYS connected whether I am using the 12v umbilical from the tow vehicle, the power pedestal, a generator, or no other power source besides the solar.
(I do have a disconnect switch between the solar panels and the solar controller. It doesn't "transfer" to anything else, just kills power to the controller.)