Originally Posted by Guessed

Attached is a sample document done with mapped content controls. For this demo I've used built-in metadata fields - if you have a lot of these then you would need to embed a custom xml since you will run out of built-in fields quickly.

If you don't want to use mapped content controls, you would need to use macros to populate the secondary content controls. Code for that can be seen in various threads here including most recently this one https://www.msofficeforums.com/word-...-dropdown.html