[vinix]

I also ran into this problem in Sigil 0.9.9. I have to manually run "Tools -> Epub3 Tools -> Generate NCX from Nav" everytime I added a chapter.

I tried the trick @mrprobert offered, but even if I use the file generated by ePub3-itizer, Sigil didn't update toc.ncx automatically, still.

Why syncing toc.ncx and nav.xhtml must be run manually? Does it mean toc.ncx is not needed for epub3 and I can delete it without any compatibility problem?

I found that if I opened such a epub file in Moon+ Reader, it will read the content of toc.ncx rather than nav.xhtml, and the result is some of the chapters can not be accessed.