To reformat a document so that it matches the formatting of a (modified) template, create a new document based on the template and then import the existing content via the Insert File dialog box (Insert tab | Object | Text from File).

By the way, if you are trying to change numbering formatting by changing quick style sets, note that it will be unpredictable. When numbering is involved, using templates is the way to go.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional

Well, I may have used the wrong word. I'm using a template that contains the styles I've created (and placed at the different levels in the multi-level numbering in my List Style named "Headings" that's saved in the template). I select the proper style (and hence the proper outline level) from the available styles, and the ones I use mostly are in the Quick Style Gallery (at the top right of the page, where the commonly used styles in the template are so they can be quickly found). And I used the style inspector to step through the document, and every paragraph in the document uses the right style. So these that are numbered out of order are paragraphs formatted with heading styles that are within the template and are all attached to the List Style at the proper level.