Hold down the Option key and drag the top node (with all nodes selected) to the bottom of the editor canvas
--> This will have placed new nodes "off" the canvas below the bottom edge of the viewer window
Have you been able to reproduce the problem?:
●●○ — The problem occurs sometimes, but I haven't found a way to specifically cause it
Have you found a workaround?:
redo the select and drag with new nodes and the seems to fix it.
I would expect that editor zoom level data would be stored within the file in the same manner that node location data on the editor is, the way notes are, etc.