The Atlantis Control Board can be resized with the mouse if you

The Atlantis Document Bar can be resized in the same way by capturing the edge which is closer to the document window.
But there is more to these "resize" edges of the Control Board and Document Bar. Instead of pressing the left mouse button when you get a double-arrow pointer, you can give a double-click instead. This will automatically hide the Control Board or Document Bar. To bring them back on screen, use the commands of the View menu.
See also...