Really? I did it before and it worked perfectly fine. it just gave me a warning that it was made on another device and it might include malicious code. But other than that it worked fine.
There's an "Upload/Download Saves" feature in the game, but for that up- and download need to be coordinated (it only goes through the Ren'Py server and saves are only kept for one hour). Otherwise, from what I've heard/read people complain about, saves transfered "manually" have started getting blocked entirely since a certain Ren'Py update, not sure which.