The Loop Data COP is only used within a Loop COP subnetwork. Its purpose is to provide access to the previous iteration’s output image for the Loop COP. The first iteration will receive the image data from the Loop COP’s first input; all other iterations will receive the previous iterations' output.
COPs within the Loop subnet should use its output rather than connecting directly to the first subnetwork connector.
This COP should not be created on its own (it will not do anything).