Global moderators used to be a volunteer role that allowed you to ban/timeout users in any channel.

All global moderators were removed in 2018 and there's no sign that global moderators will be added back in the future.

https://blog.twitch.tv/en/2014/12/17/chat-update-new-global-moderator-role-and-badge-c58dc6867463

https://blog.twitch.tv/en/2018/12/13/thank-you-global-moderators-4d44cfccf22