Many heading levels are a document designer's nightmare, because there are only so many ways to differentiate headings - - chiefly typeface, size, indentation -- and using all the possible connections quickly looks cluttered.
And that's three in total, including any title, sub-title, or chapter title that will be listed in the To C.
Fortunately, Writer is also flexible enough to allow you to produce useful, aesthetic To Cs if you follow a few basic steps.
However, before you read about these steps, you might want to refer to "Open Off-the-Wall: To Cs, Indexes and Bibliographies in OOo Writer," which covers the basics of how to create a To C. you create the markers to use in the To C via Insert - Indexes and Tables.
It will force you to work through styles and Writer's other automated features.
At first, if you aren't in the habit of using styles regularly, you may think that this work flow is a nuisance, but you will soon find that it helps you regularize your work habits.