Remove built-in search-engines in Firefox Nightly I don't use the default Firefox search-engines, so I like to be able to delete all the Amazon, Twitter, Google nativelly installed on every Firefox version. 

Using current and beta version of Firefox, I am able to remove built-in search-engines on Firefox on Android, simply from the add-ons manager and disable the search-engine. 

However, on the last Nightly build, the search-engines can not be found in the add-ons manager. My phone is not rooted, so I'm not able to directly set the search-engines list by editing the files or removing it through the search-engines list. Can't find a property in about:config either...
In the current Firefox 28 the issue is solved by setting browser.search.loadFromJars to false in about:config. Then only the search engines I added myself are shown.