Thanks. I saved Doc A as a macro-enabled Word template, but I didn't know you had to save it to the default C:users/.../templates folder. Anyway, I've fixed that and managed to attach it to Doc B. However, the normal.dotm styles are still showing in the Quick Styles Gallery/Styles Pane in Doc B. I wasn't sure how to get Doc A styles to appear so selected the only thing I could see that made reference to Doc A: Change Styles > Set as Default for Doc A Template. It didn't work.

To clarify, you do not need to save it to that folder and may not want it there. For a full exploration of templates, their uses and placement, see Templates in Microsoft Word and File New Variations in the Versions of Word.

I agree very strongly with Stefan's recommendation that numbered styles be set up following How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly. It is step-by-step and all of the steps are necessary. It may be that by following those directions, you can reproduce the numbering setup of your other document. Once you do that, save a copy of your revised document (with the content cleared) as a simple outline template for future use. The first time doing this it is confusing and seems a lot of work. Saving as a template means you never have to repeat that work.