Since footnotes are so rarely used in fiction, it wasn't really worth it for that alone. However, the framework I've added will also be usable for adding highlight comments/annotations for Open Document exports too. It is also usable for a new story structure feature I've been discussing with a few other people.
The footnotes feature was one of the oldest remaining features in the backlog. Over 4 years old. Good to get it done finally too. 😊