I am a non-coder at this point, thus I am seeking GUI oriented solutions:
The relative scaling of the global bounding box in relation to the contents / curves / cursors changes when the display is zoomed and this seems like a fundamental problem. Why should the global bounding box be tied to he display zoom? Certainly a graphical editor needs to be able to zoom in and out of a curve in order to make GUI oriented adjustments without having the scaling of values change every time one zooms in and out of the display.
The local bounding boxes do not have this problem, however, how do I then create a local bounding box that can be shared by multiple curves / cursors?