I started digging through your code and I think I have it solved. In summary, I'm changing the actions validateUrl and getUrlParamIds to account for the reverse ordering. I'm also changing the workflow presentation to reverse the order as well to account for child to parent moving from left to right vs. right to left.

I'll post a summary of what I changed as soon as I get it working and if anything obvious sticks out as a possible concern you will likely know right away.

Thanks!