I know of a few kidney donors who later donated a liver-lobe. It is still rare, and many hospitals will not even consider it. Liver donation has a much higher risk of complications and hospital re-admissions than kidney donation. At present there is more traffic at the FaceBook page of Living Donors on Line than there is here, and the question has appeared several times there, and some kidney-and-liver donors have responded with information there. You might want to go there and scroll through past entries on the topic, and then post there also if you wish.
Fr. Pat