Thank you for your reply. Indeed, using the relative tab is an option but I was indeed asking about exporting an upscaled version of the output image (I hope I'm using the right words !). Because when I export with relative, it does not keep this "pyxel art" thing but larger than 256x256.
And what you've suggested could be interesting by making GIF !
Concerning the UI/UX, I feel like a "help" button into the software could be an option, but else I guess that's good :)
Have a good day !