Search something in a new tab, without switching to the new tab. Like highlighting something and searching on a new tab, but without opening the tab, and instead of highlighting you type what you want to search.
For when you are reading something and think of something you want to search afterwards. Then i open a new tab, search for it, so i don't forget, then go back to previous tab to continue reading.
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You can already do this, though it is a bit hidden.
Type your search in the address bar, and rather than simply clicking, hold down ctrl + shift (on Mac its command + shift) as you click.
That should open in a background tab. If it opens in a foreground tab, try only holding down ctrl (or command).