Tree model diagram: can you have disconnect nodes?

I have a tree model diagram with the following definition:

myDiagram =
  $$(go.Diagram, "myDiagramDiv"
, {
  "undoManager.isEnabled": true
  , allowDrop: true

  , allowDelete: true
  , allowCopy: true
  , "grid.visible": true

  , layout: $$(go.TreeLayout,
	  arrangement: go.TreeLayout.ArrangementHorizontal,
	  arrangementSpacing: new go.Size(25, 25),
	  alignment: go.TreeLayout.AlignmentBottomRightBus,
	  angle: 90,
	  layerSpacing: 50,
	  rowSpacing: 10,
	  setsPortSpot: false

when I drag nodes onto the canvas (from the palette) they automatically jump to a position the first level and when I interactively link them to a parent they take their correct position.

However I would also like to have floating nodes (such as document nodes) that are not part of the tree at all. How would this be acheived?

If you don’t connect them with another node, don’t they operate the way that you want?

Or are you asking how to prevent those disconnected nodes from being laid out by the Diagram.layout? Set or bind Part.isLayoutPositioned to false. But because the layout won’t arrange them, you’ll need to assign their position or location yourself somehow.

If they will never be connected with links to anything else, you could use a simple Part rather than a Node.

Perfect. Exactly the hint I needed!