Is it possible to remove and restore Walk-behind areas, just as we can remove and restore walkable areas? Maybe by just changing its baseline via a script?
That's exactly how it works:
https://adventuregamestudio.github.io/ags-manual/Globalfunctions_Room.html#setwalkbehindbase
You can also use a non-clickable Object instead and turn it off.
Thank you again, Khris. I was searching for that function, SetWalkBehindBase, but couldn't find it. I have solved this in another way but this is great to know for the future.