Graph legends for violin plots

I think the legend shows the style of the trace lines (the data points are just a 'bonus' and can also be disabled). So you rather want to make the trace lines different. Go to Graph => Modify Violin Plot and set different colors. If you want to fake the display of the markers you can also use the Special => Marker and Special => Marker Color in the Modify Annotation dialog to approximate the markers manually in the legend.

It seems that the default legend is an open square with the color of the violin trace line. And it shows the fill color, if any. I didn't notice this at first, because I kept all trace lines black with differently colored open circles as populations. Initially, I found the square unintuitive to relate to the violin, at least if not filled. But I see the problem - there are many possibilities to shape the graph. 

I don't know if it's feasible: How about a flag to set the default appearance for the legend to e.g. lines/fill (as now), data points, mean/median? 

It seem the trace is the only non-optional element of a violin plot, so it makes sense to use this for the annotation. I guess different display modes need to be implemented for violin plots for this to work (similar to normal plots). You can try to write in the feature requests forum or directly via email to WM. But then I think maybe an annotation is less relevant to violin plots, since they are displayed in categories anyway, no?

If anyone can suggest a useful way to represent a violin plot in a legend, I am listening! Further complicated by the fact that you can make different settings for each sub-plot of a violin plot trace.