Show Position Nodes not working for loaded Interpolation .mitk projects.
The DataManager should ideally display new nodes as child nodes of the annotated segmentation node but it the checkbox does nothing.

Steps:

1. Draw and modify segmentation masks while the 3D interpolation is activated
2. Without clicking “Confirm”, Save the current scene with “Save Project”.
3. Close Project or Close workbench, doesn't matter.
4. Load the previously saved *.mitk-file to the workbench.
5. The segmentation tools and the “Interpolation” area are available again.

The selected interpolation mode shows Disabled instead of 3 dimensional .
And, more importantly, Clicking on "Show Position Nodes" checkbox does nothing.

OS: Windows 10 (not tested on other platforms)