When GT4T is running, ctrl+d is added into all applications/programs as a shortcut to fetch translations from Glosbe.
Select a word anywhere in any application, and press Ctrl+d, you get a popup list of translations from Glosbe or Linguee or WordReference (which you picked at the setup screen).
Then use UP/DOWN arrows and Enter to insert the translation of your choice. In this way, you get translation suggestions without leaving the app you are working in. And the translation of your choice can be inserted where you are typing to save your keystrokes.
Download and install GT4T here and try it yourself! When GT4T is running, select the word below and press ctrl+d,