Descendevator
You know what? This question by the American sort of makes sense. British folks call an elevator a lift, even though it moves up and down. You can’t lift anything downward, can you? So, why not just call it an elevator like the good ole citizens of the Land of the Free?
Then again, you can’t elevate anything downward, either. Hm… It appears that we’ve found ourselves in somewhat of a linguistic pickle here. We need to combine our brainpower together to come up with a directional-neutral name for them. Let’s try calling them up-and-downers from now on.