you go to the settings aka the grey gear near a side, then you press it, the button on the top of the box where you can save/upload a file, click or tap the paper with the down arrow, then you can upload it with the paper with the up green arrow, but you'll have to go back to the old editor to get the file again to make the gradient

RIP, it works on chromebook and comp, so you'll have to get either of them then- ;-;