How to: table of contents
 

Is it possible to create a table of contents with Sigil so when the epub document is opened on an eBookReader it is recognized as a table of contents?

So far I still end up with a toc.ncx file which has no content at the <navMap> tag ...

Are you using the TOC Editor? Sigil creates TOC entries from heading tags (e.g. <h1>Chapter 1</h1>). An easy way to create a new heading is to type some text and then select the heading level from the drop-down combo box.

You can see the what the TOC will look like in the TOC editor. You can also change which headings get included, and from version 0.1.4 (which is not out yet, but should be along shortly) you can change the heading text, too.