these are the possible solutions I found when working with similar
problems:
1- Handling the position of the new element in the NewElementViewFactory,
using layout constraint on the View:
Node node = getViewService().createNode(...)
BoundsImpl bi = (BoundsImpl) node.getLayoutConstraint();
bi.setY(5);
bi.setX(250);
2- Modifying the CreationEditPolicy installed in the EditPart in which you
insert that new element. It implements this method:
protected Command getCreateElementAndViewCommand(
CreateViewAndElementRequest request)
3- Listening for the notification of the new addition in the
handleNotificationEvent() method of the parent EditPart