I don't have a dehydrator but know many people who do dehydrate liver with no problems. I've read that the secret is to make SURE it is completely dry. Any moisture will foster mold.
I would slice as thinly as possible. With squishy organ, I'd make sure it is frozen almost solid and use a very sharp knife in order to get it very thin. Then dehydrate completely.
To be safe, I'd probably just store it in the freezer and take out a piece when needed. I bought some dehydrated kidney awhile back and I just keep it in the freezer. Brody gets one for a treat a couple times a week and he eats it straight out of the freezer with no problems at all.