Add/Remove part(s) from existing cutting plane

It might be useful sometime to remove or add (a) part(s) from a selection set cut by a cutting plane.

To do so, both the cutting plane and the part(s) to be added or removed must be selected (use the Ctrl key for multi selection).

Then, while clicking on 'apply to a selection set' in the cutting plane menu press on Ctrl/Shift to Add/Remove the part(s).