In DBT Version 12.2 upward, templates are distributed as ordinary text files instead of in binary form. (However, they still retain the ".dxt" file extension.) Though you do not normally need to edit DBT's template files, advanced users (who are familiar with what is in the template and what they need to change) may find reason to do so.
You may edit a DBT template using any simple text editor (such as Notepad on Windows or TextEdit on the Macintosh) to make changes.
It is important to appreciate that the templates in the DBT Templates folder should not, themselves, be changed. In fact they cannot, because this is a protected system folder. So, when a user edits a template, the result must be saved as a new file in a different folder.
You are encouraged to save the resulting template in one of the folders used for custom templates made via the Document: Create Template function.
A custom template for your own use is normally saved in your own computer profile.
~/Library/Preferences/Duxbury/DBT/Templates.