Hi there :-) W.r.t. FireFox 77, I need to know if the 'Open Menu' button on the far right of the default installation is PROGRAMMATICALLY customizable ? I want to remove it as part of hardening the browser for a desktop application that must be accessible via the Internet. While I respect the fact that client-side hardening is not best practice, let's not go there please :-) I have successfully used userChrome.css, but I don't want to have to place this file manually nor manually set the 'toolkit.legacyUserProfileCustomizations.stylesheets' preference to 'true' on all the client machines, but rather manage this centrally on the server side as is possible with autoconfig.cfg together with the autoadmin.global_config_url preference setting. Is it possible? I have also tried specifying the 'browser.uiCustomization.state' in the autoconfigfile.js file changing the default 'about:config' setting from this >>> {"placements":{"widget-overflow-fixed-list":[],"nav-bar":["back-button","forward-button","stop-reload-button","home-button","customizableui-special-spring1","urlbar-container","customizableui-special-spring2","downloads-button","library-button","sidebar-button","fxa-toolbar-menu-button"],"toolbar-menubar":["menubar-items"],"TabsToolbar":["tabbrowser-tabs","new-tab-button","alltabs-button"],"PersonalToolbar":["personal-bookmarks"]},"seen":["developer-button","webide-button"],"dirtyAreaCache":["nav-bar","toolbar-menubar","TabsToolbar","PersonalToolbar","widget-overflow-fixed-list"],"currentVersion":16,"newElementCount":10} to this ('pref') format >>> {\"placements\":{\"nav-bar\":[\"stop-reload-button\",\"customizableui-special-spring1\",\"urlbar-container\",\"customizableui-special-spring2\",\"downloads-button\"]},\"dirtyAreaCache\":[\"nav-bar\"],\"currentVersion\":16,\"newElementCount\":10} but while the other controls are removed, the 'Open Menu' button as well as the 'Back' and 'Forward' arrows are not removed even after restarting Firefox. Is there another preference that should be used to remove or hide at least the 'Open Menu' button? Thanks for your help. APB