Me too Mario. The manual is less than clear about the registration question.
Here is what I know so far. Set up and tweak the registration of your choice. Then, hit the Digital Record button to the left of the screen.
It will give you 3 options. Hit Style Creator. Hit Next to go to the Assembly tab. Then hit the J button to Save.
From there, you can save to User or hit Next to save to Floppy. Then hit Next twice to return to the main screen and you will notice the saved style is currently loaded.
That's it. It will save Style, Tempo. However, I have not been able to save the voices I selected for Main, Layer and Left..or Key Changes.
Maybe someone can pick up where I left off.