Typically it doesn't make sense to draw on a render window with any interactive segmentation tool, if the render window geometry is not aligned with the reference image geometry (see T16132: Allow segmentation with several images).
In order to work with the mxnMultiWidget, we removed the geometry-comparison with the 3D render window, happening inside the QmitkSegmentationView. Instead the geometry is compared for each render window that the mouse entered. This allows to have different render windows with different geometries without disabling the UI of the QmitkSegmentationView for the whole workbench.
A first draft, showing a simple text overlay (warning message), was created in {D727} and {D730}. In order to go for a more cleaner approach we want to provide an interactive overlay widget that allows to perform some action, e.g. resetting the geometry for the corresponding render window.