I've got this object which exists of 10 meshes or so. Their UV maps are all different, of course. I would like to have the same shading on all of them, so I created a node group. The node group includes the normal map. I wish to resize the normal map. For that the Mapping Node can be used. The mapping node is also part of the node group. What I would like to be able to do is, reuse this node group entirely, and be able to set a different scale, on a single axis, per instance of the node group (or per material is you will).
I didn't get your question, do you mean you want to duplicate the node group to different materials? ctrl+c and then ctrl+v in new material's node editor would work but I think you have to enable the "copy attribute" add-on