hey, i do use this sometimes. its good vs. stationary targets. the problem with this is to make bombs hit at the same time, or moveable units will move out of the way of the second and third bomb, once the first has gone off.
Multi Release kind of helps with this a bit, if targets are close to each other.
i did try this at home, and i was able to create a new CAS page record, hit use, select it as T1 and use this Target for the JDAM.
going to try around a bit more, see if i can make multi targets work via the CAS page.