As someone who fairly often encounters 150+ page Word files that need to be washed through a disinfectant bath of .txt … if most of the formatting in the original is headings and lists, it can save time to tag them before you start.

Example: open the navigator, go to the first level one heading, type in <:h1> (or some other likely-to-be-unique string) as a prefix; skip to the next level one heading and repeat; loop for other levels of heading. Lists I do by eye; body text is easier to prefix <:body> in a text editor. You may be able to extend the technique to graphics and captions, depending on how you've implemented them.

Save the file out to plain text, bring it back into Word and use search/replace: use the Styles options to apply the heading and list styles, then [No formatting] to delete the tags. Have fun!