Access this from the Scan pane by selecting a profile, clicking Settings, choosing the SET panel, enabling Auto-crop and clicking the associated button.
Auto-crop width
Select small, medium or large margins, to be applied to all images scanned
with the current profile.
The horizontal and vertical values are as follows:
For small margins 40 and 50 pixels
For medium margins 80 and 100 pixels
For large margins 120 and 150 pixels.