Right, the Shared Shader should never show up at all. It is of no use to you as a user, it's purely an under-the-hood thing, and allows one map to be connected to multiple slots in a material or even into multiple materials. So definitely never create one, and for any materials where it shows up in the native C4D editors, I'd suggest using the Corona Node Material Editor to edit it instead (it would be the only way to get a proper look at how the material is set up).
(BTW we have a task set up to remove it from showing in the dropdown list, just as it was removed from the right click in the Node Material Editor - so we'll make it so you can't create one manually in the future. Meantime, don't :) )