Optimizing spritesheets usually eats up alot of time. Something that might save time however might be to add options/functions that allows user to toggle some additional coordinates (as mouse coordinates, doc size and selection size at the bottom).
One that would be useful in my particular workflow is Display Selection Coordinates, maybe with additional sub-options such as - from pivot, - from top left, - from bottom right, - from center e.g.
My current workflow in the extrapolation of coordinates in spritesheets usually is just me using the mouse coordinates. A bit tedious and time consuming way of doing it (and not the best way possible I’m sure )