I may not fully understand the nature of your query so I will answer based on my understanding of your goal.
> You have a group of nodes displayed and have established locations that are good for each node.
> You collapse the group of nodes.
> When you expand the group later, the location of the nodes is not the same as it was before the collapse.
If this is the correct scenario, I suggest that the "Locked" vertex property feature could help.
Select the nodes in a group that are in the correct location *before* collapse.
Right click and select "Edit selected vertex properties".
Set the Locked flag to yes.
When you collapse and later expand the group your nodes should be where you left them.
If this is not the solution to your problem, please follow up and I will try to address your concern.