Use Gimp Online to edit an image in Google Photos

[Ofnuts]

Maybe you can copy/paste the picture between two Chrome tabs, one open in Gimp Online and one open in Google Photos (not too likely though). Otherwise to have Gimp-Online be able to update the picture in GooglePhotos, you would have to give some random site your Google credentials because it would have to masquerade as yourself. Probably not something you want to do. Security and ease of use are rarely compatible