I discovered that if I activate the feault admin interface (not admin2) and activate the option about which I speak in my first post, then if I come back to the admin2 interface, the option is available ;-)
Pascal
Ce qui embellit le désert c'est qu'il cache un puits... quelque part... (A. de Saint-Exupéry) - http://luxpopuli.fr/eZ-Publish