This might not be correct, but i'll have a try...
When you add the ip address of the device in "add new node", have you tried selecting "No Status - External Node".
You can add the device into NPM and not monitor its status, but also allow the option of adding it to NCM (Standard tick box selection).
That way, it will show up in your NCM application and you can go into it to add the SSH credentials.
Of course, the status part wont work, but i think you can still backup configs...
Again, dont quote me on that, but may be worth a try?
