I am using two monitors and now I seem to understand how it works with the mouse.



- Between screens it only works via Keyboard.



- On the outer lateral sides, I have to drag the window past the frame (part of window "disappears, goes out of the screen") then the Peek highlight appears and if I drop the window it is resized to fit the half screen.



- Upper Peek (which seems most unnecessary as double click is faster to maximize window for me) I have to drag for a longer length the upper part of the window touching the upper frame of the screen for peek to activate.