To make onion-skin in After Effects.
For example you have a layer with mask animation.
When you run a script it duplicates the layer twice and shifts one layer a keyframe left and the other keyframe right. Then it puts both duplicate copies in mode Multiply and opacity 50.
So on the screen you see previous and next position.
How about that ?
I do it manually sometimes, but if a script could take care of this, that would be really great