Disable creation of new nodes

GoJS
1

I found that if I press “CTRL” and drag an original node, a new node will be created just like the original one, but I don’t want to allow any new node, where do I disable this feature?

2

You are talking about the behavior of the DraggingTool to allow users to make copies of selected Parts. You can disable that specific behavior by setting DraggingTool.isCopyEnabled to false:

$(go.Diagram, . . .,
  {
    "draggingTool.isCopyEnabled": false
  })

For more discussion about the various possibilities, please read GoJS User Permissions -- Northwoods Software