Hi Kawashima,
You can programatically add the symbols and links to the diagram. Please refer to the following Forum link to achieve this
http://www.syncfusion.com/support/forums/message.aspx?&MessageID=57502
You can also set the line label's value to the link's'width.
link2.Labels.Add(new LinkLabel(link2, "2"));
link2.LineStyle.LineWidth=Int32.Parse(link2.Labels[0].Text);
Please refer to the attached sample and let me know if you have any questions.
Thanks,
Nagaraj
FlowGraphics.zip