any one know if tht possible to do this in the control rig ?

in the last live stream Epic made about the control rig they being asked the question many times about importing an existing animation from the skeleton to the controls rig controllers just like how we do in HumanIK in maya to adjust the controllers and the ik different parts of the body . but the answer was just how to move and add another additive keys on top of the FK skeleton even the additive value to the rotation for a an arm as an example .but actualy no one asked about that because we can do that simply in any animation window by adding additive keys to any none .the question was about adding additive keys to the controllers on top of an existing animation . any one know if tht possible to do that in the control rig ?