You will need to install a user script manager extension to install this script.
This adds a verbatim tick-box to the DuckDuckGo search bar. It works from main DuckDuckGo home-page only.
Tick the 'Verbatim' box and type something, such as...
search as a phrase
When you search this will automatically be wrapped in quote marks...
"search as a phrase"
Use this UserScript to form your initial phrase for a search. Then in the top search-box on the results page you can add additional search keywords and knock-outs, with reference to a quick glance at your initial search results.
Useful for those with old hands, or who just want to avoid too much "keyboard yoga"!