Hello Subashni 

Thanks for your investigation, I have seen this topic in the help document. The way I understand material libraries in Discovery however is that you are able to provide a shared material library (let's say on a network folder) and point to this folder in the settings. All users will then have the same materials. 
The mentioned "User Defined Material Libraries" will be used if a user changes some properties of a shared material and saves his copy in his own User Defined Material Library.
I've tried this and it creates a MyLocalMaterialLibrary.json file. Maybe there is a way to rename this to "shared..." and save it to the predefined folder as shared library? But then again Discovery tries to read a XML-file, so maybe the shared library should still be a XML- and noch JSON-file?
It would be nice if someone could give us a hint on the expected file name and format. 

Have a nice Weekend!

Kind regards