Sun Dec 30, 2012 8:25 am by lax
Assuming you have created your 3 Action Target Groups, and each of them has 10 Characters in it...
If what you want is 3 different buttons to toggle broadcasting mode, then use the Mapped Key Wizard and have it create a "Broadcasting Toggler". You can pick which windows will broadcast to which other windows as part of this wizard. For example, you might have "Group (all of): Group A" broadcast to "Group (others in): Group A" (and likewise, B to B and C to C).
If what you want is for the default Shift+Alt+R toggle to set up the independent broadcasting groups, then in the "Activate Repeat" mapped key under the "Always On" key map, create Repeater Target Actions to replace the default one that resets the current window's broadcasting target back to "Window: All w/o current". Repeater Target Action is exactly what you'd be configuring with the Mapped Key Wizard when you select "Group (all of): Group A" broadcast to "Group (others in): Group A", so same thing here.