Currently, the TOC will display an entire paragraph of text based on the Paragraph Style. I've assigned a unique Character style to give distinction to the first two sentences of the paragraph using Nested Styles within the Paragraph Style.

In the attached example, you'll see that "Subject 1. Setup." has a distinct Character style, this is the only text that I want to appear in the TOC. Perhaps there's a way to accomplish this. But It would be nice to have the option to populate text based on Character Style only.