Offline means no communications outside the device. It does not mean no communications inside the device. So unless the device has had its network stack completely disabled, should should have no problems running other services over the mentioned protocols.
Even if the networking stack is completely disabled you can still use Pipes - these are rather easier I believe on UNIX than on Windows but still should be possible.
Regardless, it is pretty easy to set up a Python server that will communicate over any of the above protocols and so your Python "server" can talk to Node-RED and visa-versa even without external networking of any kind.
By the way, I'm now starting to write a blog post about comms protocols available to Node-RED with their relative strengths and weaknesses. Probably won't get finished and published for a week or so since I have other things to do but at least I've made a start. The subject is coming up a lot at the moment.