if one Geodesic or Loxadrome is drawn the undo stack is cleared of previous ones because There Can Only Be One (TM Highlander). Ideally it should redraw previous geodesics or loxadromes.. this requires more complex handling.
Consider keeping several geo/loxa curves on the screen at the same time.
elondaits
commented
7 years ago 
if one Geodesic or Loxadrome is drawn the undo stack is cleared of previous ones because There Can Only Be One (TM Highlander). Ideally it should redraw previous geodesics or loxadromes.. this requires more complex handling.
Consider keeping several geo/loxa curves on the screen at the same time.