Under the Menu Contents tab, Pages/categories to exclude. When I enter a page to exclude, the page id is not saved and the page is not excluded from the menu bar. It was working fine in 2.2.3 . Version 2.3.x has seem to have broken it.
Also I noticed if you upgrade from version 2.2.x to version 2.3.x all of your settings will be deleted and the default settings will put back into place. I would avoid this version for now.