When creating new one-off messages, you may have noticed this 'Load from template' button. This allows you to load pre-written SMS or email templates, saving you time.
To create new SMS templates and have them ready to fire, click Marketing > Marketing Templates > SMS.
Click New Template
Name the message (for internal use) > describe it (also internal, optional) > add the message content and Save.
You'll now see this message available when clicking 'Add from template'.