You are able to place multiple balloons on a device which has multiple balloons defined for it:

If you select the Insert Balloon option for a selected device, the Insert Balloon dialog displays all of the balloon defined for the device. You have the option of placing all of the balloons at the same time which will group the balloons together:

Once the balloons have been placed, they can be individually selected and repositioned if desired:

Restriction: Currently, if you select all of the balloons and reposition them using the Move command, the balloons will return to the original configuration (the image to the left above).