Cancel when external objects are dropped

As i can see dropping of external objects can’t be rejected.
Could you implement this feature within the next releases?

You can arbitrarily change the dropped selection in a diagram listener, for example:

  myDiagram.addDiagramListener("ExternalObjectsDropped", function (e) {
    var newnode = myDiagram.selection.first();
    if (newnode.linksConnected.count === 0) {
      // when the selection is dropped but not hooked up to the rest of the graph, delete it

That code is from:

If you are talking about dragging from another Diagram/Palette, you can set Diagram.allowDrop to false. (That is the default value, actually.)