Problem: You need to create a device that has more than one circuit on it. Modular furniture is one common example of a device that needs to be modeled in this way.
Solution: Create a receptacle type to represent the device. Create multiple loads on the receptacle type.
When you circuit the receptacle, you will be prompted for which load to connect. Connect each load to a separate circuit.
When you draw a homerun from the device, you will be prompted to select the load. You can draw a separate homerun for each circuit, or select all of the loads to draw a combined homerun for the circuits.
You are limited to 4 loads connected to 4 different circuits. If you need more circuits than that, you will have to model the device using two receptacles.