Ok, call off the search, I solved the issue in a very manual way: if you ‘View Source’ on the homepage and search through BLDR’s raw HTML, you can then identify the ID tags that BLDR has inserted for each section already!
Only snag is that these don’t appear to be editable anywhere, so your anchor links end up looking a bit weird (e.g. #pg-636-2), but nobody really analyzes their URLs anymore right?
If anybody else has a better solution, I’m all ears still! Thanks 🙂