2
Currently, the configuration categories do not support a parent-child relationship.
I agree that it would be more clear to the user in your case, but the way forward may be to create an authentication module with plugins (and module config categories) for the different authentication methods.
"When you can flatten entire cities at a whim, a tendency towards quiet reflection and seeing-things-from-the-other-fellow's-point-of-view is seldom necessary."
Cusix Software