I ma not too sure if this functionality is avaiable in the new release of spark. Is it possible to broadcast a message to users from 2 different groups. I have been using spark in conjunction with the wildfire server and it works great.
One option for the UI is in the Broadcast Message window, have a little “+” icon next to the group name you can click on. When you click on it, a window with a list of groups appears where you can select or deselect groups for the message to go to. The Broadcast Message window should of course reflect the list of groups selected.