With KiCad 8, arbitrary shapes can be connected to nets. Instead of the Inkscape hack with adding line segments to approximate curved traces, this can now be done natively.
The s-expression for the curves are like this:
(gr_curve
(pts
(xy 66.4748 93.278) (xy 62.7248 90.378) (xy 64.2748 96.428) (xy 61.012077 95.482793)
)
(stroke
(width 0.2)
(type default)
)
(layer "F.Cu")
(net 7)
)
That ends up looking like this:

The four sets of points will end up looking like this in Inkscape:

With KiCad 8, arbitrary shapes can be connected to nets. Instead of the Inkscape hack with adding line segments to approximate curved traces, this can now be done natively.
The s-expression for the curves are like this:
That ends up looking like this:

The four sets of points will end up looking like this in Inkscape:
