Yes! This is the answer. It's clear that reading the Bookdown book from start to finish should be on my 'to do' list. I really appreciate you sticking with me to guide me to a solution. At present, these labels are not working as desired for bookdown::word_document2 (perhaps they never will), but they work for pdf_document2 and presumably html_document2 (haven't tried). Next up, refining the placement and size of figure images in my document...