All the materials stored in the “User material database” can be renamed.

The name of materials stored in the reference material database cannot be renamed. If needed, they can be duplicated as illustrated in the previous section.

How to rename a material?
1 Click on the material label you want to rename (click on the right mouse button)
2 Give a new name in the dedicated dialog box.
Note: The new name must not already exist in the material database, even for another type of material.