Hey, this is really cool. I think rounding of corners on the polylines might be broken, at least it doesn't seem to work in any of the demos. I'm running v4.7.2.stable.mono.official on a macbook. 

Below is a polyline with "Join" "round" and subdivision 20. Seems it has outlined the rounding but not filled it in.

Okay fixed the regression, this was Godot only I broke it when I was working on better anti aliasing, thanks for reporting!

Also you're totally right I forgot I had the logo scene to reference haha