Looking at the question Has in-space refueling been done?, it looks like all fuel transfer operations in orbit have been done with room-temperature hypergolics. Has on-orbit transfer of cryogenic fuels ever been demonstrated, even as an experiment?
No. (Unless it has been done as part of a secret mission.) NASA's Space Technology Mission Directorate had plans for just that called Cryogenic Propellant Storage & Transfer (CPST), which would have launched a mission to demonstrate both the transfer of cryogenic propellent, and its storage in space for a long period of time.
Unfortunately it was cancelled for cost reasons, and replaced with a ground-based investigation.