Hi,

TreeLayout always places child nodes on level below their parent. If you need to place first leaf node to the right of its parent, you could implement it like this:

using System.Linq;
...
CreateTree();

// set IgnoreLayout on first leaf node in branch
// so that TreeLayout does not reserve space for it
var firstLeaves = FirstLeafNodes();
foreach (var node in firstLeaves)
	node.IgnoreLayout = true;

var layout = new TreeLayout();
layout.Type = TreeLayoutType.Cascading;
layout.Direction = TreeLayoutDirections.LeftToRight;
layout.LinkStyle = TreeLayoutLinkType.Cascading2;
layout.Arrange(diagram);

// align ignored nodes to their parent vertically
foreach (var node in firstLeaves)
{
	var r = Parent(node).Bounds;
	r.Offset(r.Width + layout.LevelDistance, 0);
	node.Bounds = r;
	node.IncomingLinks[0].UpdateIntersections();
	node.IgnoreLayout = false;
}

List<DiagramNode> FirstLeafNodes()
{
	return diagram.Nodes.Where(
		n =>
			n.OutgoingLinks.Count == 0 &&  // a leaf node (no children)
			Parent(n) != null &&
			Parent(n).OutgoingLinks[0].Destination == n)  // first child of its parent
		.ToList();
}

DiagramNode Parent(DiagramNode node)
{
	if (node.IncomingLinks.Count == 0)
		return null;
	return node.IncomingLinks[0].Origin;
}

void CreateTree()
{
	var root = diagram.Factory.CreateShapeNode(defSize);
	var secondLevel = CreateBranch(root, 4);
	foreach (var node in secondLevel)
		CreateBranch(node, 2);
}

List<DiagramNode> CreateBranch(DiagramNode parent, int numChldren)
{
	var children = new List<DiagramNode>();
	for (int i = 0; i < numChldren; i++)
		children.Add(NewChild(parent));
	return children;
}

DiagramNode NewChild(DiagramNode parent)
{
	var child = diagram.Factory.CreateShapeNode(defSize);
	diagram.Factory.CreateDiagramLink(parent, child);
	return child;
}

RectangleF defSize = new RectangleF(0, 0, 20, 12); 

If you need to arrange whole branches in different direction than overall tree, you could achieve it by applying TreeLayout independently for these branches, grouping them, and running TreeLayout for the main tree using KeepGroupLayout option.

I hope that helps,
Stoyan