I made a command in my game where you can block a certain user's text from ever being displayed on your screen, but I don't know how to create a new savefile on the client's end with world/New() to store the blocked users, so they can unblock them later and etc. Any help?
You wouldn't create a client savefile in world/New(); the reason being the client hasn't logged in yet. =P You'd want client/New(), most likely.

Look up Import() and Export() in the reference for information (and an example) about client-side savefiles.