Here's another report, same OS 10.8.5 as I have. Must be an unresolved bug. I hope the developer tracks this forum.
http://code.google.com/p/sigil/issues/detail?id=2417
Meanwhile, good suggestion to try 0.7.2 since 0.7.4 has issues for Mac. No quitting with older version (!) and I am closer except for new major problem. Here is what I get now:
(1) HTML Table of Contents with subheads is fine.
(2) The desired abbreviated and bulleted list of major headings is generated fine; HOWEVER …
(3) The NCX navigation no longer corresponds to the "toc.xhtml" bulleted list. When I select "NCX View" in Kindle Previewer it just says "Start"; and on the Kindle itself the 5-way controller only selects the start page (the TOC with subheads); it does not navigate between the major headings per the bulleted list.
Any thoughts?
P.S. I just checked, and (as with v0.7.4) the numbered list does not have the same problem; NCX View and navigation both behave as desired with major headings. The only issue is the aesthetic appearance of a numbered list instead of bulleted -- clearly the lesser of evils, and one of personal taste, but an odd outcome nonetheless.