Global fields are added to all types in the GraphQL schema, which renders its visualization unwieldy:
That's why the configuration (see next section) offers to not expose the global fields (when doing introspection), by either:
Exposing them on the Root type only
Not exposing them at all
Please notice: Global fields will still available under all types from the schema, even when not exposed; in other words, they are simply "hidden from view" when doing introspection. If you desire to actually remove (not just hide) some global field from the schema, this must be done via an Access Control List.
By default, the schema exposes global fields under the Root type only, and it is easier to visualize and browse: