A search found that Shift+Win+arrow key is supposed to switch the active window between monitors. However, that key combination switches between virtual desktops, not between monitors. Anyone know of a correct way to switch the window that has focus between monitors via a keyboard shortcut?
Switching between virtual desktops is <Ctrl><Win><Arrow>. <Shift><Win><Arrow> is the key to move app window between monitors.
If you've somehow reprogrammed these, try just <Win><Arrow> - the window will end up on the other monitor after couple of pressings.