Basically, Firefox allows you to set a keyword (which I often set to an abbreviation + question mark) which you can link to a site's search URL. For example to search Google Scholar I would type my keyword, "sch?" and then my search query, and after pressing enter I am taken to the site's search results. It's a few more steps you have to take, but has the added benefit of allowing you to add the functionality for any site.
https://www-archive.mozilla.org/docs/end-user/keywords.html
Basically, Firefox allows you to set a keyword (which I often set to an abbreviation + question mark) which you can link to a site's search URL. For example to search Google Scholar I would type my keyword, "sch?" and then my search query, and after pressing enter I am taken to the site's search results. It's a few more steps you have to take, but has the added benefit of allowing you to add the functionality for any site.