I know I've suggested a similar feature, but all this talk of smoothing curves brought this up in my mind; in addition to a tool to smooth a curve, Affinity Designer should also have the opposite.  I am of course referring to Midpoint Displacement, which would allow illustrators to make non-uniform curves more easily than having to draw each node individually.     Being able to smooth curves is indeed important, but as it is, it's really hard to produce a line that doesn't look uniform, and a roughening tool to add pseudorandom midpoint displacement would make illustrating much less time-consuming.