Transform (stretch) all drawings on all layers/frames

I need to change the scale of all drawings on all layers and frames of an animation. Of course I could scale the layers in the transform options or put everything into a symbol/peg but I would like to avoid that because I have to continue animating and would rather not draw into a distorted holder.
Is there any way to achieve that? I tried the “edit multiple drawings” option of the selection tool but it doesn’t seem to work. It always only edits all drawings on all layers on only one frame.
I would be very glad if someone could help me.

You can turn off the Animate button and then use your Transform tool, and it will adjust all the keyframes at once.

~Lilly