Thank you for your review. You can type on the URL bar, but you have to precede your text with an 'a' (webextension api requirement), i.e. 'a g text_to_search_in_google'.
Also, there are two hotkeys defined if you don't want to click the icon:
Alt+q: open the input box (same effect if you press the icon)
Alt+w: open a new tab with the input box.
For more info check the 'About this extension' box on this web.