Yes, that was my opinion, too. but when there is a left and a right distribution, to what does the Box-Whisker plot refer?

Anyway, in the attachment you find a solution based on two AreaSeries showing the same distribution on the left and right side (just a quick test - it can be optimized, I'm sure), and an overlay BoxAndWhisker series showing the 1%, 25%, 50%, 75% and 99% percentiles.

So you see: there is not dedicated ViolinSeries, but it can be composed by other series rather easily. Most of the work is needed by the math to calculate the distribution.