This actually gets nasty, because you would have to write out a text-only file (the ACD file) of the data for submission to the standalone ACA/HB system. Then, you would have to write a script (such as in Python, Java, or similar) that would modify this file properly to collapse the two levels into the same level.
Maybe somebody out there knows how to mess with Lighthouse Studio files to actually trick Lighthouse Studio into doing this. But, I don't.