Till Firefox 3.0, it was very easy to add a new search engine. One just needs to click on Manage Search Engines, and then click on Get More Search Engines. It would display around 30 search engines, and we need to select one and it would be added.
Starting from Firefox 3.5, they made it complicated. If you select that option, you would get hundreds of options, and it becomes very difficult to find the correct one.
I wanted to add dictionary search engine, and I have done the following for this.
Installed Add to Search Bar.
Opened the website, Dictionary.com.
Righ clicked on the search box, and selected Add to Search Bar.
It got added, and I can search in dictionary from firefox search.
We can do the same for any other website/search engine.