How to use a layout doLayout sub nodes

we will use more layout work tegether in a diagram.
I define a root node,then expand some subnodes.
and then,i only want the layout to layout the expanded subnodes,but all the nodes.
how to get a new position to avoid overlapping each layout.
In short,We use diagram more in expanded nodes and find the relation of each node so we can get some infomation useful!!
Now,we want control the layout position arbitrary,and we want control the node arbitrary.
how can i do?tell me!
Thank you!

I moved this topic from the GoDiagram forum.

Even with a tree layout, adding children may require moving many and sometimes all of the nodes in the diagram. So only moving the children really isn’t sufficient to produce a good result.

But if you want to control the position of each node yourself, you can. Don’t set Diagram.Layout at all. Implement your own positioning of the children relative to the parent node.