The Physics behavior's Start = When Triggered applies to all Dynamic-tagged layers that are controlled by that behavior. In your case, you want each ball to become dynamic at different times, so you'll need to apply a separate Physics behavior to each ball (which means each ball will need to be in its own group, since only groups can have behaviors.).
Make sure each Physics behavior has Start set to When Triggered, and each ball-group is triggered by a different key. Since the local Physics behavior overrides the settings of the top-level behavior, this also gives you the ability to change the weight/friction/bounciness of each ball individually.
Yes sir! That's the ticket, it's working exactly like I want now. It was applying the Physics behavior to each ball (group) individually that I had not yet thought to attempt. Thank you so much not only for suggesting the correct rigging to do what I wanted, but for explaining WHY it would work. Perfect! Thank You!!
We're considering changing it so that it works the way you expected it to. That would mean that each Dynamic-tagged layer that is also triggerable would have independent trigger-ability for physics. But the current scheme would continue to work.
Another thing we're considering: separate visibility from triggering. So you could trigger physics and have the layer be visible before it's triggered. Currently to do this you have to have a duplicate of the layer without Dynamic tag, and use a swap set to hide/show the non-physics layer at the moment the physics layer is shown/hidden.
That sounds like it would be easier. Thats the exact process I'm working with now, making a bottle cap pop off a beer bottle. One copy of the arm with bottle closed with a swap set for a hidden arm with bottle open... I can't wait, this program keeps getting better and better!