I'm treating this somewhat like a support question as with the current system I think you can largely do what you're asking, though it's a manual process. Let me know what you think.
After a search, for example "stealth killing", that query remains in the search box which you can continue to tweak as desired‡, say to "stealth killing [deus-ex-human-revolution]"
Note that if you add a search term in square brackets [], it will be interpreted as a tag, even if it isn't popular enough to automatically be so. Check out the search page for more methods to improve your queries.
‡If you tweak too fast; more than 6 searches in 1 minute, you get rate limited.
