Search engines are added to Firefox search bar. As your list of search engine grows, you may want to sort the order and place the maximum used search engine at the top. Here’s how to change the order in which the engines are shown in the Firefox search bar.

Type about:config in the Firefox location bar.
Type browser.search.order in the filter.
Now change the values as you wish to reorder.

For example, to make Yahoo as the top engine and Google just next, make the following changes:
browser.search.order.1 = Yahoo
browser.search.order.2 = Google

Your response: