I want to be able to graphically pick the joint center points while I am defining them
In 2013, you have to either manually type the midpoint coordinate or let the software do it for you automatically.
Another option for "picking" the coordinate of a universal joint is to create the joint using either of the options, and then use the "Draw > Modify > Point Move" command to relocate it to the desired point. But this is only a workaround at the moment.