@lassoan The feature in the animation you previously uploaded is very different that what was in the original post from @christeen. What you presented was just a dynamic “scale bar” which gives the user a sense of “zoom” but not “position” which was identified as the objective. I also have a use case for a more versatile vtkLegendScaleActor https://discourse.vtk.org/t/legend-grid-annotation-from-paraview-12-with-vtk-filters/13479/3 and as a formal proposal here LegendScaleActor SetModeToFocalPlane . Additionally in the example animation from @christeen the way the ticks/numbers respond to zooming in/out is much prefered to the default behavior of vtkLegendScaleActor.
I believe that improvements here is not wasted effort in that the user experience as described and illustrated by @christeen is not readily achievable with existing implementations.