The shape decorators are painted on top of the shape that owns them, so you can try bringing that shape to Front of the ZOrder or send to Back the connectors.
Each shape has the BringToFront and SendToBack methods so it should be relatively easy to adjust your Z Order.

Best Regards,
Nevron Support Team

I've created a diagram with simple shapes joined by NLineShapes connectors. The shapes each have a NShowHideSubtreeDecorator to allow child shapes to be collapsed.

If one of the line connectors between shapes overlaps or is near to the +/- shape of the decorator, I find that I cannot get the decorator expand/collapse action to fire. I'm guessing this is due to the connector line being above the decorator in the drawing z-order?

Any suggestions on how to keep the decorator on top?
Thanks
Andy