If as I understand some (all?) formatting is contained in or associated with paragraph marks, is there a way to "read" what formatting is present in a particular mark?

I working on editing a 100+ chapter story that has been converted from a PDF to .docx. After editing I use Calibre to covert the .docx to .awz3 for reading on my Kindle Paperwhite. During conversion a Table of Contents (TOC) is generated from the chapter headings. Of the 100+ chapters some show in the TOC and some don't. If I then edit the .docx to copy a working chapter header and paste it over a non-working header (and renumber it), the former non-working chapter header will now show in the TOC upon reconversion. This is not really practicable for 100+ chapters so I'm hoping to "read" the formating and figure out the difference between working and non-working chapters.