It seems to me you're using the term 'master document' to mean something other than what it means for Word. In which case, the link Charles provided likely isn't relevant.
If you want to link contents from multiple documents together, that can be done via Word's INCLUDETEXT field - which is what Word creates for you if you use Insert|Object|>Text from File>Insert as Link. See:
Field codes: IncludeText field - Office Support
Word also provides an RD field which allows you to have a Table of Contents in one document that references content in another document. See:
Field codes: RD (Referenced Document) field - Office Support
You may also find
https://www.msofficeforums.com/word/...nal-files.html helpful when using INCLUDETEXT & RD fields to link documents that may need to be moved around.