How to open and organize materials libraries
You can do the following:
When you remove a user library from the Materials Browser, the library file remains on the hard disk. You must manually delete the library file to reclaim hard disk space.
You can add the material to multiple libraries.
You can remove a material from an unlocked user library using one of the following methods. Locked materials cannot be removed.
The material library panel lists material libraries that contain matches for the search phrase you entered.
Objects that use the material are highlighted in the drawing area.