Hi the_terrible,
You can go on the last frame, then press CTRL+SHIFT+L
to add the needed keys if you hadn't already.
Press spacebar to deselect everything, therefore see all the timelines in the dopesheet.
Select the white keyframe by clicking on it, this will select all of the keyframes beneath it, then press CTRL+C
to copy them.
Create a new animation and paste them using CTRL+V
Done!😃