It is NOT a (inline)TOC
unless it has the semantics set properly
You can not set more than 1 semantics per file. Thus,
the file must be separate.
Sigil makes following the rules, easy. If you use its tools to make the Cover, TOC, you get valid code.
Drag and drop, allows you to change the arrangement.
Spell check will only verify that the word has bee spelled correctly, not that is the correct word.
A good Proof Reader is needed