itch.io

I have a better workaround: Export to gif then crop, like you said, but then use a Gimp script to make a spritesheet from the layers.

Ex.:

registry.gimp.org/node/20943

https://gimper.net/resources/simple-sprite-sheet-maker.574/

When you have your spritesheet, you can reverse the process by making guides along the cutting lines between frames and then Image -> Transform -> Guillotine.