New answers tagged browser-add-ons
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.
Use either the Habit Browser or Slepnir Browser apps. They both support Userscripts. I had to tweak my scripts slightly to get them working (they handle events differently) but they both work really well.
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