Hi Roee ,
Thanks for your interest in Syncfusion products.
If your intention is to connecting Connecting a link to the same node then you have to create the Connectionpoints and you can connect them.
Please refer to the attached sample that demonstrates this completely.
http://websamples.syncfusion.com/samples/Diagram.Windows/F70401/main.htmPlease let me know if you have any questions.
Thanks,
Nagaraj