Glad to see this is in the feature request as my company also needs this functionality. It's currently causing issue with new hires. Even though they aren't assigned to all Brands/Dept/Groups, when they create a ticket, call log or live chat, they have to navigate a very long list of Departments and Groups.
This has been causing many mis-entries into incorrect groups and departments. And like above, we would love to be able to give a customer agent access to view tickets and reports without seeing Brands they are not associated with.