Hello,
I don't know how you set your keyframes already, but if there is no position property set in each keyframe, meaning that you only have opacity animation or color animation, but not position animation yet,
just changing the position of the very first keyframe should move all the rest keyframes.
But if there is already different position set in each keyframe, this workaround does not work.
Currently, editing multiple keyframes at once is not supported in GWD.
Thanks,
Mariko (GWD team)