See visualizers for more information on visualizers.
Render hooks are wrapped with generic visualizers at load time and are toggled on and off via their wrapping visualizers. Generic visualizers associated to render hooks are always loaded as Scene visualizers and cannot be deleted or changed into Global or Node visualizers.
Generic visualizers are also used to represent any other type of visualizers with corrupt or unrecognizable data or parameters.
Duplicating a generic visualizer wrapping a render hook does not duplicate the hook and produces an empty visualizer shell with no function.