Hi,

WPF needs some time to update the visual tree if it's very large, so for diagrams with thousands of nodes you will need to use some sort of virtualization. You might try the VirtualizingDiagram control installed with WpfDiagram (see Virtualization sample project), or implement your own virtualization by removing and adding items dynamically when the viewport changes due to scrolling or zooming.

Alternatively you could create a bitmap image to show your circuit-diagram graphics and create actual diagram nodes only as interactive editors when you detect mouse is over some part of the diagram image. When users finish modifying a node or a link, update the bitmap and remove the interactive items to keep the WPF visual tree small.

I hope that helps,
Stoyan