Xara does provide a limited capability with its Contour tool:

Click image for larger version.  Name: Xara - Curved Join Inset Path Countouring.png  Views: 97  Size: 158.5 KB  ID: 133829
For complex, concave and convex cornered shapes, the method is to apply an Outer Contour of 4px with the Join set as Round. You then click Inset Path.
You do the same with an Inner Contour to this new shape with a smaller Contour Width, again Round Join and Inset Path.

The end result is larger. You cannot use this approach to get different sized curves.

Acorn