The Visibility column is added to the Libraries tab of the Materials tool window. Click an icon in this column in order to hide a corresponding library or a folder of a library.
You can Show invisible items using the contextual menu of libraries list.
In result, all elements will be displayed regardless of their visibility. Click an icon in the Visibility column in order to make a corresponding invisible element visible again.
You can switch back to the default representation, where invisible elements are hidden, using the Hide invisible items command in the contextual menu of libraries list.