To save screen space, you can selectively hide shells you are not using. To hide a shell, click on a selected shell name in the Browser Instance or Class list on the left of the Main Window. The shell name is unselected and the shell is hidden.
Note: This does not effect whether the shell is managed, and so visible, when you generate code. See question on "How do I gain control over the display of these Dialog boxes?" if you are trying to control when a particular shell is visible in the actual application.