The Prog Change tool lets you generate program change messages. There is a separate menu button for each of the 16 MIDI channels. When you press these buttons, you will see the General MIDI patch list. When you select a patch from the list, the appropriate program change message will be transmitted on MIDI output.

Although the default list of patches is intended for use with General MIDI synthesizers, you can change the list of patches by editing the lib/maps.k file (there are comments in that file that explain what to do). The functions in maps.k are used by several KeyKit tools (e.g. the Group and Kboom tools also use the program and drum maps specified there).