Apps similar to Search Engines Helper include Add custom search engine, which is free and open source. Other options are Wutsearch. Between them they cover Mac, Windows, Linux and the web.
Free and open source extension for adding a custom search engine to the list of available search engines in the search bar and URL bar to Firefox or a desktop browser that can use Firefox extensions.
Wutsearch is a palette of the best search engines. A frictionless search launchpad that requires zero extra clicks. Simply type your query in any search box and hit enter to open the results in a new tab.
