Converts a polyline (EdgeCollider2D coordinates) to a PolygonCollider2D points using the given thickness.

PolylineUtils.cs

class PolylineUtils {
    /*
     * Converts a polyline to a polygon with the given thickness.
    */
    static Vector2[] GeneratePolygonFromPolyline(float thickness, Vector2[] points) {
        if (points.Length < 2) { return points; }
        Vector2[] result = new Vector2[points.Length * 2];
        var normal = Vector2.zero;
        for (int i = 0; i < points.Length - 1; i++) {
            var direction = (points[i + 1] - points[i]).normalized;
            normal = 0.5f * thickness * Vector2.Perpendicular(direction).normalized;
            result[i] = points[i] + normal;
            result[points.Length * 2 - 1 - i] = points[i] - normal;
        }
        result[points.Length - 1] = points[^1] + normal;
        result[points.Length] = points[^1] - normal;
        return result;
    }
}