temp1 picture - Look at the frames I want to move.
temp2 picture - Select the frames I want to move.
temp3 picture - Drag the frames a few frames to the left. Notice the extraneous empty keyframe made in the lower layer.
I know I can avoid the extraneous empty keyframe by dragging the top layer separately then dragging the bottom layer. But this is too time consuming when I want to move 20 layers in this same tedious way. How do I drag all layers at one time without creating extraneous frames after the layers are dragged?