I tried to make that feature before release, but with webextensions, i can't find a way to get the default search engine to use it. I could use google by default, but not everybody uses google, so for now you can drag the text to the address or search bar.
I neither want to use the old addon sdk because it's going to be removed :/
After thinking a little bit, i could make an options page to set the query url of the search engine the user wants to use, but dunno if it is worth the effort