Window docking messed up

I don't know how I did it, but my docking has changed and I can't get it back the way it was.

My Project Explorer was docked on the left edge of the screen with height being the main window height.
When I opened my Immediate window it would be docked on the left side below the Project Explorer (the Project Explorer would shrink to make room for the Immediate window).
When I double clicked the top bar of either window it would undock and take up most of the screen, and when I double clicked the top bar again it would return to the same docked position.

Now no matter what I do I cannot get the Immediate window to dock below the Project Explorer. It always docks beside the Project Explorer and both heights are the main window height.

Hello,

this is tricky, since it's not intuitive. With all window undocked and the code window showing: drag the project window to the top left edge of the screen, just below the menu bar. Look out for a dotted line that shows the future position of the window. It should be displayed as a tall rectangle. Release the mouse button.

Next, drag the Immediate window underneath the Projects window, releasing it near the horizontal scrollbar of the Projects window. Watch the dotted rectangle. It should be underneath the Projects window.

See attached screenshot.

cheers

Thanks;
You're right, it definitely is not intuitive.
Where do you learn these kind of things?

Here!
.....