Hi @drbsg ,
if you are looking for a “destructive” way (assuming you do not copy the data you are displaying), the Image Pixel Access of this thread might be what you are looking for.
As far as I know, we dont have any custom controls for Python, but as you have access to the imagedata you can use whatever UI Framework you like (I assume).
Thus handling overlays is something you might want to do with the tools of whatever UI Framwork you use.