Merge Measurements
Main Menu: Measurements > Merge Measurements (flatten image)
Merges all the measurements with the image.
After measurements become part of the image they cannot be separated or modified in any way.
If the image was not saved you can use Revert to saved to get back the measurements (as editable objects, separated from the image background), but if the image was saved after merging the measurements, there is no way to get back the measurements.