Aside from the docs below, are there additional filter details ?

https://gmic.eu/tutorial/command-guide.shtml
https://gmic.eu/tutorial/index.shtml

For example, where are the descriptions for parameters in the latest "Kaleidoscope [Polar]" filter ?

eh,eh I think most users just fiddle with the sliders and numeric values and see what changes in the preview window.
Maybe the filter author has some material somewhere on what the filter is doing.

BTW 'toasteroven' is a cool nickname like 'teapot'. LoL

I only just got into this forum as I am not a GIMP user, but that being said, I am the author of that filter. Also, as you can see, I have made over 40 filters for G'MIC now, and many of them are based on PDN filters.

Angle Cut defines the duplicates along the X-Axis. Just play with the slider, and you'd note that the x-axis is the circle.
Radial Cut defines the duplicates along the Y-Axis. Again, just play with the slider, and you'd note the duplicates of concentric circle.
Surface Angle defines the angle of the polar distortion. It's more obvious with a non-even integer angle cut value.
Angle Edge defines how duplicates are defined within the x-axis.
Radial Edge defines how duplicates are defined within the y-axis.
Conical Start only is used to quickly modify the angle without playing with the surface angle.

Sublevel defines the quality of the polar filter.
Interpolation defines the end result of the rendering of polar filter i.e how non-integer values are interpolated.