You can select multiple keypoints on your screen by swiping them all at once using the Animation Path Tool. Or by holding down shift and then just selecting the ones you want to move. Once you have the key points selected that you want to move, make sure that you rest your pointer on one of the selected point to move them all. If you don't you will be adding a new key to the line instead.
I hope this helps.
Europe, Middle East and Africa