I've done that but there is only 2 blank tiles where my 2 saves should be.
Try to make a new save in the new game first. Joiplay will then create a save folder where you can put your saves. Thats what I did first, because I couldnt find the directory for the datas first.
Dang that sad to hear, sadly I dont know any workaround for this. But honestly fresh start isnt that bad. Especially when a old save is used from like 1y+ its cool to do a fresh start because some early events got changed.