Code

Arrow currentLink = null;

private void fc_BoxClicked(object sender, MindFusion.FlowChartX.BoxMouseArgs e)
{
  PointF mousePos = e.DocumentPos;

  if (currentLink == null)
  {
    currentLink = fc.CreateArrow(e.Box, mousePos);
    currentLink.Dynamic = true;
    fc.Capture = true;
  }
  else
  {
    currentLink.Destination = e.Box;
    currentLink = null;
    fc.Capture = false;
  }
}

private void fc_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
{
  if (currentLink != null)
  {
    PointF mousePos = fc.ClientToDoc(new Point(e.X, e.Y));

    currentLink.ControlPoints[currentLink.ControlPoints.Count - 1] = mousePos;
    currentLink.UpdateFromPoints();
    fc.Invalidate();
  }
}