Hi Toril,
You can assign the "Fade In/Out" function to one of the Assignable buttons or to the "Rotary Sp/Assignable" button or to a Pedal. Please refer also to page 136 in the Genos Reference Manual ("h0" V2.10).
Press [Direct Access] and then the desired button to open the Assignable display. The Fade In/Out function is in the Style category of the assignable functions.
Best regards,
Chris