How do I dynamically change the fromSide or toSide value?

Diagram
#1

How do I dynamically change the fromSide or toSide value when an item is moved without fixing the direction of the connecting line?

#2

You may try to use the update() methof of the dataCollection:

to update the properties of the item.
Like:
https://snippet.dhtmlx.com/t1mgihrp