I perhaps made this more difficult than it is. I missed the command "Add to the Quick Styles Gallery" when right-clicking on the style name in the Styles Pane.

Here are some additional references I've located:
How to control the Quick Styles gallery on the Home tab in Word by Shauna Kelly
How to Place Your Styles in the Quick Styles Gallery by Dan Gookin
Make Word's Quick Style Gallery Work for You by Susan Harkins
Working with Styles by Tony Jollans