according to wiki page
Is it useful?
The reason why I ask is because I never use this parameter before and have no idea how we should expose via GUI. ( I am trying to merge the timetrack and keyframe panels)
This is very useful!
increasing a keyframe length will shift all the further animation to a later time. It is one essential task of any animator! 
-G
Very useful indeed. For moving adjacent keyframes and rescaling keyframes/waypoints. (So no remove form GUI 
)
Currently we have seek to previous/next keyframe function exposed in GUI. That is fine. But how about waypoint? Is it a reasonable feature requirement?
Hello zohaaa and welcome here …
About Waypoint future of … there is a particular thread… hope you like it