This area displays, in graph form, the CAPI elements of the current interface.
By default, the graph is laid out from left to right. The main interface name is shown at the extreme left, and the layouts and elements defined for that interface are shown to the right. The hierarchy of the layouts (that is, which elements are contained in which layouts, and so on) is immediately apparent in the graph.
An item selected in the graph can be operated on by commands in the Object menu in the Interface Builder's menu bar. This menu contains the standard action commands described in Performing operations on selected objects, as well as a number of other commands described throughout this chapter.
To remove a layout or pane from your interface definition, select it in the graph area and choose Edit > Cut or press the toolbar button.
LispWorks IDE User Guide (Windows version) - 25 Nov 2011