Currently you can add a vertex to a balloon leader, but once added, there is no option to delete a vertex.
The "Delete Leader" option only works if you add another leader between a component and the balloon.
One must perform several workaround steps or delete the balloon and start over.
Thanks,
Jerry
P.S. Yes, I know you can press BACKSPACE to remove a vertex (click) while you are creating the balloon, but this request is for an existing balloon.