I think I figured out a way to do this.
Right before the <h1> heading I added the following code:
Code:
<div style="display:none;" >Unique Text To Search For In Chapter 1</div>
Then I used the Index Editor to add an entry that searches for "Unique Text To Search For In Chapter 1", specifying the Index Entry that I want it to go into.
When I create the index, the code I put in changes to:
Code:
<div style="display:none;" id="sigil_index_id_1">Unique Text To Search For In Chapter 1</div>
and the link in the index entry that I specified takes me to "sigil_index_id_1".
I just need to make sure that the text I used is unique in the book so that it only finds one occurrence of it.
This appears to work fine for the index, and the unique text does not appear in the book or in the TOC on my readers (FBReader and Ebook Viewer from Cabilbre).
The key is using the style "display:none" to make the unique search text invisible. I have put the style into a class I call "DGInvisible". Then, I can simply add the code
Code:
<div class="DGInvisible" >Unique Text To Search For In Chapter 1</div>
and add a search entry to the index and it works.
Thanks to everyone for the suggestions.