Shape Legend not displaying in Charticulator

[bh2115]

I've used both the PowerBI plug-in and the browser version of Charticulator with the same result.

I have created a custom visualization that binds data to the shape and color of the points on the chart.
I can add a legend for the color, by opening the bind data menu of the attribute and clicking add legend. This works perfectly fine.

But doing the exact same thing in the shape attribute does nothing. When I click "add legend", nothing happens.

I've tested removing the color legend in case it's a limiting factor, but even with no other legends on the graph, the shape one won't appear.

I've also tested other attributes such as stroke color and those appear fine, even with the original color legend there.

How can I fix this issue?

[zBritva]

@bh2115
The first part of the visual is approved and available on Appsource page