This doesn't work for me. In fact, it looks like the option and command modifier keys behave just the same, i.e. they move the selected point around. I've also tried all combinations of control, shift, option and command modifiers, to no avail.
Picking up any of those predefined z-shapes from the factory “line types” stencil doesn't let me reveal their control handles either: what am I missing?
I've sent mail to
omnigraffle@omnigroup.com but only got an auto-reply... Any suggestions?