Bookmarked URLs in Firefox can be invoked by providing them a unique keyword. These keywords you add are called smart keywords in Firefox. That is because, if you type the keyword in the addressbar and type Enter, the corresponding bookmark URL is loaded in the browser.
If a website offers search by using the GET method, then that is supported by Firefox bookmark keywords too. For example, consider a website that can be searched using
http://libraryABC.org/books/?booktitle=%s. If you add this URL, with the
%s in it, as a bookmark with keyword
library, then you can search this library for the term
newton by typing
library newton in the addressbar.
Firefox takes this one step further. You can add right-click in any search bar on a website and choose Add a keyword for this search and Firefox automatically adds a bookmark with the keyword you provide.
I find it useful to add such smart keywords for private websites like Confluence, JIRA and bug database used inside workplaces.
Tried with: Firefox 74.0