2-fered fixtures

I'm probably looking right past it, but I'm new with my hedgehog 4, and can't figure out how to enter a dimmer that's 2-fered. I can duplicate the dimmer by adding a second "50", then "50.1" in my list for instance, but then I want to reorder the 2-fer (50.1) so it follows, oh, let's say, 120. By default it just follows 50. I wouldn't matter except I need it that way in the plot I'm drawing. Hopefully this is something super simple and it's just newbe-itis stopping me from seeing how to do it.
Thanks in advance!