I agree with Graham (not Greg) that you would be way ahead of the game doing a custom template.

You would likely want to work with the export file Word Customizations.exportedUI.

The following page may help you understand the xml structure of these.
https://msdn.microsoft.com/en-us/lib...tomizationFile

Notepad is the program I would probably use to try to make changes to these. Keep backups.

TheCustom UI editor only works on docx, docm, dotx, and dotm files for Word.
The XML Notepad program will not read the file.

I do not know of anyone experienced with Office ribbon modification that would recommend bothering with the files generated by the interface, but you are free to do it the hard way.

The thing is, these files are not really appropriate for sharing. When you transfer one to a new computer you overwrite any existing modifications using that file.

Modifying the Ribbon in Microsoft Word
RibbonX: Customizing the Office Ribbon by Robert Martin, Ken Puls, and Teresa Hennig