On your Cloud9 button layout, Group Broadcast buttons are labelled with a unique icon.
A Group Broadcast to multiple counterparties is initiated by simply selecting a Group Broadcast button. When selected, the broadcast button and all assigned counterparty connections are illuminated to give the user visual feedback on who they are actively broadcasting to.
You can dynamically add or remove counterparty connections to the Broadcast Group on a one-off basis. Simply right-click the button and check or uncheck the relevant box as required.