I've been trying to document the simplest way to create an ebook with a tool that most folks already own. The tool I've chosen, Microsoft Word, is a bloated, impossibly complicated piece of software that for some inexplicable reason, is used by a huge proportion of the populace. Feel free to enlighten me about its virtues in the comments.
Anyways, I want to call your attention to one particularly important failing of Microsoft Word for Macintosh: it will only create linked or active TOCs if the TOC contains page numbers. It's really important to include linked TOCS in ebooks, and particularly in Kindle books since most of Kindle devices don't have device-generated or navigational tables of contents, but it doesn't make sense to include page numbers (since they don't make any sense in a digital landscape).
Note that Microsoft Word for Windows is happy to automatically generate a useful TOC, sans page numbers, for an ebook.
Simply uncheck Show page numbers and then check Use hyperlinks instead of page numbers.
Now look at the corresponding dialog box in the latest version of Word for Macintosh:
You can hide the page numbers, but you can't convert them to hyperlinks, and I assure you, after much testing (and confirmation from @ljndawson), that without page numbers, no page links will be created. The TOC is there, but will take you nowhere in the converted ebook.
It makes Word for Mac a much less powerful tool for creating ebooks. Of course, there are solutions (like manually creating bookmarks for each TOC entry), but it's nothing like a one-button solution (!).
Why should anyone care about how Word creates TOCs? Because Word (.doc or .docx) is the one styled format that can be read and converted automatically into Kindle format (using KDP, Send to Kindle, and by emailing the document to a Kindle device). More on that soon.