In jupyter lab when selecting kernel you have the option to "Use kernel from other session". The same functionality does not exist for jupyter notebook and I could not find any tool to achieve this.
I also looked at the jupyter REST API to see if this is possible to manually specify a kernel for the session. The most relevant section I found is Patch /api/sessions/{session} which seems to just allow changing the 'name' of the session.
Is there any way to share the kernel between multiple sessions in jupyter notebook?