I have successfully used Mobipocket Creator to add a Table of Contents to large .html ebooks I converted to various ebook formats, not just the .prc format.
What is required is to start Mobipocket Creator and then import your .html file and go to the Table of Contents section and click "Add a Table of Contents".
For the first level toc entries, choose the html tag name that identifies your toc entries and then place the attribute and value as well. For example, if all of your chapter headings are encased by a <
div align="
right"> ... </div>, then you would enter:
Tag name =
div, Attribute =
align and Value =
right.
Another example chapter heading could be <
p class="
ch_heading"> in which case you use:
p,
class,
ch_heading.
Mobipocket will alter your .html to place "id=" names and build an external toc .html file, which you could extract and place within your .html afterwards.
I used this same technique with several large ebooks I converted, the
World Fact Book and
Webster's Dictionary 1913.
Below is a screenshot of what that Table of Contents screen looks like (ignore the second and third levels).
