Orx supports multiple monitors. You can open your game on any chosen monitor by using the Monitor property of the Display section.

[Display]
Monitor = 2

This will open your game on the second monitor, not your main one.

If you specify monitor = 2 or greater than one, and you only have a single monitor, Orx will revert to monitor 1, and quietly warn you in the log output with:

Invalid monitor: index [2] out of range, max is [1]. Reverting to current monitor.