P.S. I also saw this question. Trajectory line with springjoint
The code in my above post plus what the responder wrote about parabola motion should give you what you need. You basically just need to run a “virtual ball” in “shadow mode” up until the point of release. As in an invisible ball and an invisible pivot that shadows the real ball and pivot. The difference is that in shadow mode it gets released but the real ball doesn’t. Run the shadow mode code until my code above triggers the DotProduct condition. Then stop simulating the virtual ball in shadow mode (until the real ball’s position changes, then you re-run shadow mode). Capture the velocity at release (of the virtual ball in shadow mode) and then plug it into the parabola equations you got from the first response. Use that to plot the curve.
I haven’t coded this up yet, but it falls in line with a game I want to create anyway, so when I get it working, I’ll post it here.