Hi, About:config is unavailable in the Release version of Firefox for Android but even in the Beta versions it is of limited use (as many preferences are "baked into" the GeckoView engine) and risks losing all your bookmarks and logins. If you want to leave feedback for developers, you can go to the Firefox ''Help'' menu and select ''Share ideas and feedback…''. Alternatively, you can use [https://connect.mozilla.org/ this link]. Your feedback gets collected by a team of people who read it and gather data about the most common issues. You can also file a bug report or feature request. See [[File a bug report or feature request for Mozilla products]] for details.