Is there a possible way to cancel linedef effects?

The walls scroll in a certain boss stage in my wad, to simulate falling. My plan was, when the boss dies, the platform you fight on would "land," with the floor coming up to the platform and the walls would stop scrolling to make it convincing that you've actually stopped falling, but I don't know if this is possible to do. I've scanned the wiki and I couldn't find anything that could stop wall scrolling, is there a linedef that can cancel linedef effects like this that I don't know about?

Your best hope with this may be to use linedef type 503 (Scroll Wall According to Linedef (Accelerative)), so that you can control the scrolling speed directly by moving the control sector's floor. Though be warned... last I remember that linedef type along with 502 and 504 are awkward to set up?

And before you get tripped up by it, since it's not explained on the Wiki page yet: the reason it's awkward to set up is because the angle of the control linedef is read relative to the angle of the target linedef to get the scrolling direction. IIRC, if the lines are parallel it scrolls horizontally, and if the lines are perpendicular it scrolls vertically. (I might have those two mixed up.) Angles in between those are interpolated accordingly. Hence, each unique angle on a wall in your stage will need a separate special for all of the linedefs to scroll in the same direction.

(Is that being changed in 2.2? My memory says it is, but I've been wrong about these things before.)