Golden rule - do not confuse "Headings" with "Page Headers" and "Page Footers".

"Headings" appear within the actual body of a document, such as the Title of the Topic on this page.

A "Header" or "Footer" is what appears consistently at the top and bottom of a page.

The Centering Topics here are essentially already in use in DBT in the h1. Style. Once you have understood the workings of these codes, if you wish, you can amend the existing Style, or indeed create custom heading Styles of your own.