iCalamus document windows are used like all usual OS X windows.
In the toolbar you can place some of the most important functions which are available in the menu, as function buttons.
If you want to customize the toolbar, select View menu >
Customize Toolbar
.
The dialog which then opens describes itself, and offers a list of function favorites, layout elements for the toolbar, and several view options.
All changes which you make in the toolbar will be reflected immediately after you close the dialog. iCalamus will also save these changes automatically, and keep the information about the changed toolbar for the next program launch.