Been doing a lot of really large models lately, and have noticed some things that would make life a lot easier, including "suppress" I suggested in another post.
Here I'd like to suggest a "link" icon, like the chain link icon in Photoshop, that would show that the material has been linked with another or multiples. To sweeten the deal, if you click on a link it would highlight each associated material in the tree with the now famous "KeyShot Blue".
Bill G