WikiEditor

That’ll get you a separate booklet, while the code I suggested adds pages to the existing Special Characters booklet. It probably only works when you put it in a site-wide script like MediaWiki:Common.js/edit.js, rather than in one of your user scripts.

Unfortunately, I can’t test either version at the French Wiktionary because the use of mw.toolbar.insertButton() in MediaWiki:Common.js/edit.js (under “Boutons depuis MW 1.18”) has completely broken the WikiEditor toolbar.