One thing you can do with synths that save to cassette is plug the cassette output into the sound card on your PC and record it as audio data into a file. You can then play this back into the cassette input on your keyboard. You may have to experiment a little with this to get the right level that your keyboard will accept but it can work. Just make sure you have a cassette backup first in case something screws up and you need to restore the presets. The advantage of this is that you have a backup stored on your PC for the future.