How do I make an APA 3rd level, inline heading?

I want follow APA rules for creating a third and fourth level headings. These headings are on the same line as the text of the paragraph, not above the paragraph.

Third Level Heading Example:

Third level heading. The text is here and should use a different style.

Fourth level heading example:

Fourth level heading. The text is here and should use a different style.

I can use Styles to easily insert the first and second level heading and they will show up in the table of contents. But when I make a third level heading the whole paragraph is included as part of the heading. I want to use two different styles on the same line of text.

See this tutorial: https://forum.openoffice.org/en/forum/viewtopic.php?f=71&t=709