I'd have to check to be sure, but smoothing slider probably only has effect when you are drawing a line with this tool [paint mode]

and quite lot of amount of skill and/or time is required to make it look hand drawn
in my case about 5 years before I could draw a line freehand and make it look 'easy' - skill and time is what it takes... although AI is going to help with the routine stuff more and more

I don't think you can batch it randomly, xara does not do randomisation afaik; maybe a plugin someone knows about....

if you still have a magix version you could look at the live effect > deformation filter > liquid color and use the draw setting tool to tweak your original line - with care it will look more hand drawn, but you will loose the strict equidistance between the sides which of course you do not have in a true hand drawn line outside of tech drawing where the lines do not wobble

smoothing it out is another task altogether