Clipboard Pasted

During copy paste of a node, How to get the node keys of original copied and newly pasted node, from ClipboardPasted Event

The “ClipboardPasted” DiagramEvent is documented at: GoJS Events -- Northwoods Software

The keys of the newly pasted Parts can be accessed via code such as:

new go.Diagram(. . ., {
  "ClipboardPasted": e => {
    e.subject.each(n => {
      if (n instanceof go.Node) console.log(n.key);
  . . .

Although you might be able to figure out from the node data in your particular app what the original nodes were, in general that cannot be assured. What if the user selects some Nodes and Links, copies them, deletes them, creates some more Nodes and Links, and then does a paste? The original nodes and links are no longer in the diagram (although they might be remembered by the UndoManager). There is certainly no reference from the copied nodes to the original nodes – that would cause garbage collection problems.

So if you want to know what the original nodes were, you’ll need to keep that information as properties in your node data, because those will (normally) be copied.

I need the original node only while in the clipboardPasted event. Or is there any way I can get details of original nodekey during paste?
I would not need it later, so even if deleted its fine.

As I suggested, keep track of the information yourself using your own data property.