How do I update collision polygone on event sheet?

I would like to edit poligon points, lets say, something like:

Character is walking - polygon points A

Character is crawling - polygon points B

I could make two different animations for a sprite, but I have really a lot of different animations, and this solution will be a huge pain in the ass.

Or maybe there is another, cunning way to achieve the same effect?

You currently can't. The recommendation is to use another frame.

Ok thanks.