2! Authenticator

This extension can be used in a separate window, Pop-Out Mode, which allows side-by-side viewing of your two-factor codes while additionally allowing drag-and-drop two-factor QR code input. 

Pop Out the extension by hovering your mouse over the blue title bar and clicking the launch icon.  Simply left-click and hold a QR image, then drag over the center of 2! Authenticator window and unclick.  Click "Add" to save the code as desired.