5000s: ui.key.menuAccessKey

user.js

@@ -1738,6 +1738,7 @@ user_pref("_user.js.parrot", "5000 syntax error: this is an ex-parrot!");
    // user_pref("browser.urlbar.decodeURLsOnCopy", true); // see  Bugzilla 1320061 (FF53+)
    // user_pref("general.autoScroll", false); // middle-click enabling auto-scrolling [WINDOWS] [MAC]
    // user_pref("view_source.tab", false); // open "page/selection source" in a new window
+   // user_pref("ui.key.menuAccessKey", 0); // disable alt key toggling the menu bar [RESTART]
 /* OTHER ***/
    // user_pref("browser.bookmarks.max_backups", 2);
    // user_pref("identity.fxaccounts.enabled", false); // disable and hide Firefox Accounts and Sync (FF60+) [RESTART]