Let me get this right - you are actually proposing to use a toy ... to prepare a route to go into a purpose-built navigational instrument.
That isn't right. What KCDW wants to do, I believe, is have the current position of the plane (in the simulator) output to the GPS. It's not as daft as it sounds. It lets you experiment with using the GPS during a "real-world" flight. And if you're just playing with the sim then it lets you play more realistically, if such is your want.