It's my mistake.
W2E did indeed automatically
produces an hypertext table of contents which works very well. I understand it's the easiest solution. Forgive my mistake.
I confirm that it's useless for a OpenOffice writer user to create a TOC. It would only duplicate the epub one.
I send you the book. The image is in page 2 and is totally unrelated to the book. It's just a trial.