Save lines while creating a flow diagram

Hi

I am trying to save the lines after creating a connection between the two cards, but I am unable to save those lines. If anyone can help me that would be great!!!

Thanks,
D.

Could you please, clarify your request?
What lines do you mean? Are these the shape connectors?
You can save all your diagram data to JSON string using the serialize() method:
https://docs.dhtmlx.com/diagram/api/data_collection/serialize_method/