Create a Contact Group for contacts belonging to the same Category

I want to send an email to all the contacts belonging to a certain Category but unfortunately, I can’t seem to sort or filter my Address Book by Category when addressing an email.

To overcome this limitation, I thought about creating a Contact Group for this Category but then I run into the same limitation when adding members to this group.

Is there an easy way to create a Contact Group for a certain Category aside from adding all the contacts of that Category one-by-one?