Modify transform of the previous keyframe

Is there any way to automatically apply a transform (when a property is changed) to the previous keyframe in the timeline, instead of creating a new key on the current frame? This is useful for positioning animated actors’ starting location based on their Animation position further than the timeline.

did you try to use animation montage in ue4 and fire a notify event at a specific frame,
that event can then do a simple transform to your skeletal mesh.

What I’m trying to accomplish is to being able to set the starting Transform Location of a character in Sequencer based on his position at the end of the MoCap Animation. Right now, I have to set a new Location Keyframe at the end of the animation and then manually move this Keyframe back to the start of its timeline.
It would be useful to have a setting in Sequencer that gives the option to modify/update the position of the previous Keyframe in the timeline instead of creating a new Key.