Is there a way to make my lines slightly 'wobbly' as if drawn by hand in XDPX?

[handrawn]

Yes Jono and Affinity Designers mesh tool is to die for:

could not agree more - and it would do what shipen wants very quickly and easily keeping the sides of the lines parallel, but xara does not have one

but you have remined me of the xara tool shipen could use:

select the vector line go to shape painter tool [previously called shape builder] and from the info bar drop down on the right choose warp

that will enable you to warp the line by dragging over, keeping the sides equidistant ['parallel']