C4D does not provide graphic representation of its shaders structure, neither
it allows to link one shader into several channels or materials.
Smart Shaders attempted to cope with this flaw of C4D material system :
Smart Link allows to refference one shader into any other shaders, even inside other materials.
Smart Shader List displays a list of materials and shaders - it is not yet a clean graphic representation of shader tree structure, but it is better than nothing.
Since it is an old plugin, unfortunately it does not work properly with Reflectance channel, also it crashes C4D when a link is created between channels within the same material.
It can be overcome by creating a link between a separate material channel and then by copying it into first material.