You can click the pin icon 
to pin a node so that it stays within the Node Editor view and retains its position even after a regraph. 
indicates that the node is pinned and indicates that it is unpinned.
Pinning/unpinning multiple nodes
You can select multiple nodes and pin or unpin them all at once. Select multiple nodes and then click the 
icon in the toolbar to pin or the 
icon to unpin.