Is this what you’re looking for?
To use it, select the “Hightlight” tool in the left toolbar and then “Hightlight Mode” → “Magnify” in the top toolbar.
Thanks, but it IS not wath i am looking for.
When you take a screenshot a viewfinder (with zoom) appare to select the disired selection but when you use a crop tool the slection it is only by mouse dragging without viewfinder zoom