Thank you for you response @rd2rk
So this is how your preset looks like, and I totally get this idea, it really does work:
the other options is to send A (precab) as mono to MAIN L, and B (aftercab+reverb) as mono to MAIN R
but check how the preset looks like in the John Nathan Cordy's video, do you see the two terminating outputs in both lanes on the right?:
I am trying to understand how he did that, I have checked all the settings and options, but can not find anything
I dunno, maybe it is just some old firmware, I am relatively new to Helix