Echoing Kuroyume. Materials names in the cr2 are the names of the usemtl groups in the obj file referenced by that cr2. There is no "user name" function as there is with body parts. Thus, the simplest way to change the name of a material group is to edit the obj file and the cr2. And since this is a simple find-and-replace, a text editor doesn't have to frighten anyone. Just search for all instances of the one name and replace with the other. I do wonder why it bothers you, though. This seems a lot of work for a material name you will encounter only rarely. Not only that, whatever you do will be peculiar to your own Runtime; you will not be able to legally share it without a fair bit of running around with objecation mover or the like.