Today I discovered that empty nodes aren't saved when you save a project, model or material with empty nodes in the material graph. This is strange as it's very practical to have different options for a material and the material graph is the ideal place to test out such options. I post it her as I think this may be a bug.
This also seems to be an issue with simple materials when you disconnect the nodes
1. open material graph for simple paint material
2. disconnect the nodes and save as new material
3. open and apply this saved material and open it in Material graph
then you see that's it's opened with wireframe module so this strange
Ok perfect thanks Justin