Edit your .TXT file's headings using
markdown like so:-
Code:
# My Book Title
# My Book's Author
///Table of Contents///
## CHAPTER 1
... blah blah blah ...
## CHAPTER 2
... blah blah blah ...
The single # lines will be treated as <h1> and the ## lines as <h2>.
The ///Table of Contents/// line should be placed where you want the internal TOC to be.
When you're done editing, convert the TXT file, but make sure you check the [Convert] - [TXT Input] - "Process using markdown" box.
You can read more about markdown
here
Good Luck