These commands work on objects selected with the Transform Tool (arrow) or in Objects Inspector .
These commnands are accessible via main menu > Transform > Offset in selection / transformation mode.
Expand Objects enlarges selected objects by offsetting the object contours. It is intended for creation of overlay of constant width between adjacent objects. Expand Objects command does not provide the same result as normal enlargement.
Shrink Objects reduces size of selected objects by offsetting the object contours. Shrink Objects command does not provide the same result as normal size reduction. You can use it for fill opening to make it smaller, in order to create overlay between opening and another object that covers the opening.