Specifications for the G-Major Switch Out relays:
Yes. You can, if using an external power supply, switch external relays using the Switch Out of the G-Major.
However, as the Switch Out relays are not suited for inductive loads (as relays) we recommend that a small circuit with driver transistors is added between the G-Major and your external relays.
You must at least connect a diode (i.e. a 1N4148) in "anti-parallel" and a small capasitor (i.e.100nF) in parallel with the relay coil.