Lit files generally don't have a concept of a TOC, so you have to edit the html output before doing a final conversion to epub.
I generally do this (with .6):
- Disable Splitting in the conversion dialog - disable split on page breaks and set the max split size to two megabytes
- Convert to epub
- Unzip the epub
- Edit the HTML file, insert line endings as Calibre defaults to no line feeds
- Find all the chapters and surround them by H2 or H3 tags
- Make any other adjustments merited by taste
- Save the HTML
- Zip the css file, HTML file, and any embedded images together
- Go to the edit metadata dialog for the book, import the zip file as a new format
- Open the convert dialog again
- Use the zip as the source format
- Edit the xpath to match the chapters in the book - change hx if needed to match what you used (h2, h3, h4, etc), edit the regex if needed to match the actual chapters.
- set the epub conversion option to split on page breaks
- Convert