Since the complete check list is not visible, I could be way off the mark here and others will corrcet me
My interpretation of the image above is
If icing is present and you Have N1 vibs, reduce rpm and see if that lessens the vibs
If icing is present and the vibs have suddenly increased and don't follow a reduction in throttle you probably have something worse like a missing spinner or fan blade so look elsewhere for procedures to follow along those lines.
If nil is found looking elsewhere maybe a screwed up vib detection.