I bookmark every site I might possibly want to revisit - make a habit of Ctrl+D. They're totally unsorted, but the key is to wipe the regular history on exit, leaving only the bookmarks as source material for completion. That way I can type something in the url bar and get completion to interesting sites. The url bar (or omnibox) matches on page title as well as the actual address, so it's easy, and always faster than a search engine.

if u set duckduckgo as your default search provider, you can use bang in the omibox. also you can toogle between local-area or global search. https://duckduckgo.com/bang e.g. !yt !osm !gi

Most wikis or resource/documentation sites have a local search bar on their homepage, Firefox has a feature where it lets you add a search keyword for that specific site. So if you add, say, pydocs as a keyword for docs.python.org you can do "@pydocs <query>" it looks up the query on that page.