With the current mapper implementation, PlanarFigures are only rendered when their 2D (plane) geometry matches that of a currently displayed 2D renderer scene.
When selecting a different slice, or even re-initializing the sliced 3D world geometry by means of a different dataset (so that the slice which contains the PlanarFigure is no longer contained in the geometry), it is difficult or even impossible to find/display the PlanarFigure in the scene again.
A simple mechanism needs to be devised and implemented by means of which the user can easily select and display PlanarFigure objects created in different slices.