After posting this yesterday, I did some fiddling and configuring and found a work around. Not exactly a perfect solution, but it achieves the end goal.
I have one button programed for Ditch Finish On and programed as a momentary button. Then a second button programed with the regular Ditch light effect, also as monetary, which finished with the lights off. Pressing and holding either button flashes the ditch lights, as will the blasting the horn, but the finish on button will end with the lights on solid and full and the other will turn them off.
Like I said, not perfect, but achieves the goal. Any other suggestions?