[hobnail]

Another Sigil user here. A possible trick that might be useful.

I also use the title= thing.

<h2 title="One - The storm">One <span>The storm</span></h2>

In my CSS I have

h2 span, h1 span {
    display: block;
}

This puts the chapter number on a separate line above the title, or more correctly, the chapter title is on a separate line below the chapter number. I also have additional styling to make the chapter number small caps and the title bold. The table of contents just gets the chapter title, no number.

I think it was turtle91 who shared this trick.