Overwrite?
If you don't want the diameter line, use the drawing canvas's line action instead of add poly point to draw a polygon. The only difference is that you'll have to specify the next point along with the current point, and that the number of iterations goes down by one since the last point doesn't need a line drawn anywhere.
+ System: For "steps" from 0 to resolution-1
-> DrawingCanvas: Draw line from
(x+cos((a-90)+(180÷resolution×LoopIndex))×r,
y+sin((a-90)+(180÷resolution×LoopIndex))×r)
to
(x+cos((a-90)+(180÷resolution×(LoopIndex+1)))×r,
y+sin((a-90)+(180÷resolution×(LoopIndex+1)))×r)
with rgba(0, 0, 0, 100), thickness 1, cap Butt
The example has also been updated.