[Jellby]

I would try something like:

<h1 class="hidden" title="Title Page">&nbsp;</h1>

with:

h1.hidden { display: none; }

I'm not sure how Sigil will treat that, and would avoid giving the hidden element an id (we don't want the TOC link to have a fragment identifier, a # in the URL, do we?)

Or, at least, try with:

h1.hidden { margin: 0; padding: 0; height: 0; }