Toolbar items are displayed across the top of the main window
under the menu bar and consist of a button that contains an icon.
Toolbar items are placed in a group that is shown only when its
module or toolset is current. The group also contains a separator that provides
a visual distinction from the other groups of icons in the toolbar.
The example in
GUI module example
creates a toolbar group and adds a button to the toolbar. The new button
invokes the same mode that will be invoked by the first menu item in the
example. For more information, see
Mode processing.