Now I have another suggestion, a very tiny one this time.

When I changed one of my custom nodes then it couldn't deserialize the previously saved diagram, and an exception was thrown - that's understandable.

But the Message part of the Exception object is a rather laconic "shouldn't get here". And my program catches all exceptions and normally displays the Message part of the exception as part of the message that I display to the end user.

Could you maybe replace "shouldn't get here" with a somewhat more explanatory text? OK if it is nerd-speak, just so it seems to indicate something more meaningful.

Thanks.