I added a link in the horizontal menu using subcategories and url rewrite. It works using this method http://www.templatemonster.com/help/magento-adding-page-links-in-the-navigation-bar.html#gref
Trying to add a second link there I had a different result with the same procedure.
In Url rewrite, in the Request Path I inserted the name of the page ("assistance") but there's no such page in the results.
The page is regularly published in CMS under url key "assistance"
How to find the page in URL rewrite menu?