In the design manager,
Global groups can be used in pages, and blog templates but they cannot be used in drag n drop email templates.
I have to update 8 email templates to make their footers all look a certain way. Unfortunately there's no way to create global groups. Therefore instead of spending just 2 minutes adding the global module to each of the emails I have to manually recreate it in all 8 templates and it will take me over an hour to do so.
You cannot create global groups in email templates - therefore you can't create email global groups, making it useless.
This wouldn't be as needed if there were a copy and paste group function in drag n drop templates.