As documented in the “Swing URCap Toolbar Contributions” document in the SDK, Toolbars are only support from PolyScope 5.0.0.
Hence Toolbars are not support in PolyScope 3.x.
I would suggest using an approach like in this example where the “LiveControl” JPanel is shown in a Toolbar in e-Series, and in the ProgramNode body in CB3.