I’ve just realized that there is basically only one common action you cannot do just with your keyboard (and I find myself constantly reaching for the mouse to do it), and that’s selecting a “white” word, that is, a word that has been previously marked as known. I often click on such words just to make sure that I remember their meaning correctly, even when I don’t intend to create a lingq.
How about adding a keyboard shortcut like Ctrl+Arrow (left and right) that would highlight the previous/next word next to the currently highlighted one? That should be fairly easy to implement.