Create multiple windows

Can't get this working - - I have a gemetry in one window and residuals in another. Tried the directions of dragging residuals onto white next to geometry and window doesn't go side-by-side.

What am I missing?

Should see a transparent blue rectangle

When you get close to a valid position for the window you are dragging you should see a transparent blue rectangle indicating the region the window will fill - that's the moment to release the mouse.