Hi Javi,
Thank you for your interest in Syncfusion products.
You can delete the line connectors connected to a node by iterating through the edges collection of a node as follows.
For Each con As Node In nd.Edges
Diagram1.Model.RemoveChild(con)
Next
Please download the sample explaining it from the link below.
http://help.syncfusion.com/support/Diagram.Windows/Incidents/NodeDelete/Diagram_WF_Delete.zipRegards,
Dinesh