Mostly you can add to your list of search engines just right-clicking. Why bother? Well, maybe you have a niche default search preference, but also it's extraordinarily handy for setting up shortcuts IMHO.

Example: add YouTube to Firefox as a search engine

  • Go to YouTube
  • Right-click the URL
/how-to/firefox/youtube-rightclick-search.png
Right-click menu on YouTube URL in Firefox
  • Now you'll find YouTube in Firefox settings:
/how-to/firefox/ff-search-settings-youtube.png
YouTube search engine in Firefox Search settings

If you give it keyworkd y for example, now when you type y laika party in the search bar, you'll get the YouTube search results for "laika party".