I dont think that would be possible, If you have valves in your user shapes for plant and you are trying to 'link' them in pid, you would need to move those items to the valve section in the spec. Then in plant you could use the custom valve body option and place your user shape block on top of the valve in the model.

But as for using the data from one item group (user shape) to another (valve) is not a standard function of the software.