Not having any links into the subgraph makes the problem easier, but still not trivial.
You could try a GoView within a GoControl object. Note the embedded view will need a separate GoDocument, so it's not the typical model... and things like selection may be an issue (each view has a separate selection).
You could also try building a ScrollingSubGraph class that added scrollbars (you could probably start with the scrollbar class defined by ScrollingRecordNode in Demo1) and set the clipping rectangle during OnPaint(). Things like selection might get weird in this world too... it's not without issues.
Can you send me a screenshot of your application? I’ve been playing a bit with the options I outlined above, and I’m having trouble visualizing how a partially visible subgraph is useful. It might be more obvious to me if I can see what you’re working on.