Hi Jeff,
There is no cmdlet required to create the tenant-global dial plan, it just exists by default. You can add and remove dialing rules just like you would a tenant-user dial plan that you have created.
I had debated including specific steps on how to modify/adjust the tenant-global dial plan however I decided to try to keep it as simple as possible.
If you look in the notes on slide 16 there is this note:
"You can follow the same steps outlined above for adding rules to the tenant user dial in order to be able to add rules to the tenant global dial plan. Simply use global as the identity and you can add dial plan rules to the tenant global dial plan."
Hopefully this helps to clear it up. I will likely look to add a dedicated slide on this in the future if I have to make additional changes.
Scott