handrawn, you are true, there is no way, in Xara, to simplify/smooth a line. You must convert it to a shape, then the shape cannot be converted back to a line.

It is interesting to note that even very old software like Expression can simplify a line while Xara still cannot.
So when I face such problem, I convert my file into EMF, SVG or whatever and edit it into another app, then open it again in Xara. It is not convenient.