Hey Sue,
For reflowable content, I think footnotes will probably be what you will have to do, as tedious as that sounds. The closest I’ve heard that someone has gotten to this was actually in a browser, Pablo Defendini did a comic book for Books in Browsers a few years ago that had the capability for the user to change the language so the book could be read in multiple languages, but I haven’t heard of anything being done in KF8 that does this. That being said, it might be possible to do it in iBooks in a fixed layout with Javascript.
Aaron