To Measure the Area Difference Between Elements

Select the Measure Area and Place Text tool (Drawing > Analyze > Area tools).
The Measure Area and Place Text tool setting window opens.
Select the Difference tool.
(Optional) Select Prefix, Suffix, and Text Style if desired.
Select the first element.
Select the second element.
(Optional) Use <Ctrl data point> to select further elements. The region to be measured is highlighted.
Enter a data point to place the measured area as text.

The area resulting as the difference of the selected elements is measured and placed as text.