FinderNinja

Finder Ninja is a search tool that increases your productivity by replacing the "one size fits all" approach to search -
with Quick & Efficient access to multiple search engines to suite the task at hand.

Both on your new tab page & address bar omnibox, to use a purpose specific Search Engine, all you need to do is add a "+command" in front of your query:

Usage Example:

"+file file name" will search for a file in the cnet downloads directory.
"+code code query" will search for your code query in stack overflow.
"+learn course name" will search for the course name on Udemy.
"+video cats" will search for cat videos on youtube.
"+news California" will search for California related news on NYT.

You may search freely without any commands to access the standard Yahoo search engine for any purpose.