^^^ What they said.
Here's an example:
Code:
search: <body>\s*<p>Chapter (.*?)</p>
replace: <body>\n<h1>Chapter \1</h1>\n
...although I wouldn't use <h1> for a chapter title. I'd use <h2> or even <h3>. Sigil will automagically indent your TOC based on the level of the header tag you use. For example:
Code:
<h1>Title Page</h1>
<h2>maps</h2>
<h2>epigraph</h2>
<h2>Part 1</h2>
<h3>Chapter 1</h3>
<h3>Chapter 2</h3>
<h3>Chapter 3</h3>
<h2>Part 2</h2>
<h3>Chapter 4</h3>
<h3>Chapter 5</h3>
<h3>Chapter 6</h3>
Would look like this (subject to your css styling if you also make an inline TOC)
Code:
Title Page
maps
epigraph
Part 1
Chapter 1
Chapter 2
Chapter 3
Part 2
Chapter 4
Chapter 5
Chapter 6