create new by right mouse click on a catagory name (IE: Wood)
create from an exsting to slightly modify: RMB the material to start with and copy, then right mouse click on a catagory name (IE: Wood) and paste, then modify this pasted material
That's exactly my thoughts, too. So easy once you know it. So easy to forget if you don't do it often. And new users aren't going to discover that technique intuitively.