[Jeff]

Here are two options. For your code without the group node you could replace

vizact.onkeydown(' ',bar2.visible,viz.TOGGLE)

with something like

vizact.onkeydown('1',bar2.disable,viz.RENDERING)
vizact.onkeydown('2',bar2.enable,viz.RENDERING)

the third bar will continue to be rendered whether or not the second one is

in the code with group node and the link you could add

link.setSrcFlag(viz.ABS_GLOBAL)

after creating the link. The third bar will be in the correct position and you can toggle the visibility of the second bar.