I have not, but I have read about or met a few kidney donors who later also donated a liver lobe. However, many (most?) hospitals are very reluctant to even consider such an offer, so you may have to search around quite a bit to find a program that would consider you. And keep in mind, of course, that liver-lobe donation is a much more serious operation than kidney donation, and the risks and recovery time are much higher.
best wishes,
Fr. Pat