mitk::FeedbackContourTool adds a data node to the data storage when the interaction starts and removes it at the end. The data node contains the contour as the the user is drawing.
The data node is added at the top level. This makes problems for us, because we can have multiple viewers side by side, and make a new node locally visible in a viewer only if it is globally visible *and* the user assigned it or or one of its sources to that viewer.
The solution for us would be to add this data node relative to the working or reference data. I will send a pull request.