at the very first step, input a bogus tag name that 100% does not exist so that you can bypass the "[Sphinx] already exists, use it" message
once u hit "Propose creating [wjenwne] as a new tag" you can edit the name from [wjenwne] to [sphinx]
i'm p sure if you try to use sphinx with the group label you'll get an error though, make sure to use the tag label