The polygons do not appear to be filled in CalcAreaExample.

Hello.

A quote from the documentation:

I have changed it like this and can place and clear the lines at least:

        private void OnMouseUp()
        {
            // Get the geographical coordinates of the cursor.
            Vector2 cursorCoords = control.GetCoords();

            // Create a new marker at the specified coordinates.
            OnlineMapsMarker marker = markerManager.Create(cursorCoords, markerTexture, "Marker " + (markerManager.Count + 1));

            // Save marker and coordinates.
            markerPositions.Add(cursorCoords);
            markers.Add(marker);

            // Mark that markers changed.
            changed = true;
        }

        private void Update()
        {
            if (Input.GetKey(KeyCode.LeftShift) && Input.GetMouseButtonUp(0))
            {
                OnMouseUp();
            }
            if (Input.GetKey(KeyCode.LeftShift) && Input.GetMouseButtonUp(1))
            {
                Clear();
            }
...