@Ikarus I think I just had to post publicly that I was having difficulty, because as soon as I went back to Lab 18, I passed it on my first try. X) Thanks for the encouragement! I see how your puzzle is different than the Lab 18 solution, now.

@xkydiver so the difference between this and lab 18 is that i added 3 walls here which removed the way lab 18 was supposed to be solved.
also in guides you can see my solution for lab 18.

I'm currently stumped by Lab 18, and I was hoping this puzzle would help shed some light on my situation.. but I can't figure this one out, either! I feel really foolish. Could you offer a hint or two? :)

Great level, my IQ too low, can't find the solution :D

Yep, just noticed the inability to use portals, I'm sending a hotfixed build

Seems like portal arrows don't work on this level, I'm assuming on workshop levels in general.