Saving a template to Quick Parts is new to me, as in many other features of Word. I will try it. Thank you.

Select the field, press Alt+F3. This defaults to the AutoText building block but you can choose Quick Parts as the Gallery if you want. Choose a name that you would not type ordinarily for easy insertion.

Otherwise, Insert > Quick Parts > Save Selection to Quick Parts Gallery.

Building Blocks are one of the hidden gems of Word.
Automated Boilerplate Using Microsoft Word
Where can Building Blocks be stored?