There isn't a way to add tags to app registrations specifically. As you observed, you can manually set their names to the same format, or you can add the similar types of apps to the same security group.
If you have a Premium P1 or P2 license you can also set up Collections on the My Apps portal to organize your applications.
If you'd like, I would be happy to share your insights as product feedback to the engineering team to push this feature forward.