My Pfaff also does a "quilting stitch" You use invisible thread in the bobbin, and regular thread on top. On my pfaff I can program stitches and for the quilting stitch you program one regular stitch (a little longer than you use for piecing) followed by five or six tiny stitches. You finish the programming with a repeat function. With the right tension settings you get a regular stitch with your top thread, then the five tiny stitches that bring the invisible bottom thread to the top, regular stitch, five tiny invisible stitches, etc.
The result looks as if you have spaces between your regular stitching but in reality there are five tiny stitches in between each regular stitch that you can't see. The effect gives it the appearance of hand quilting.