Hi Brad,
Good day!
Thank you for your reply.
I can fully understand your requirement, I have further checked, but currently there is no any further relevant option available to achieve your specific concern about to one keyboard shortcut.
As a workaround, currently you may perform above mentioned steps to find User Templates In File System option*.*
Additionally, in order of your requirement, if you can submit your valuable suggestion directly to our product developer team via this Microsoft Feedback portal to further development of some feature option on Outlook, our product developer team can update product accordingly in future.
I would really appreciate your cooperation. Let us know if you have any other concern.
Sincerely,
Darpan | Microsoft Community Moderator