Formatting a split heading

You have to use "TC Fields" to customize the text you wish to appear in Table of Content.

TC fields is in the hidden ribbon References that you need to unhide.

There are a few links if you google on using TC fields to create table of content.

https://wordribbon.tips.net/T013870_Creating_a_Custom_TOC_that_Includes_Portions_of_Paragraphs.html

what I found is using TC fields, means the text is very manual.  If you change your mind about the description on the body text, you need to make sure you edit the tc field as well.