Hydrogen makes it easy to convert between text files and Jupyter Notebook (.ipynb) files. You can both export text files to Jupyter Notebook files and import Jupyter Notebook files as text files. This works for any programming language for which you have a Jupyter kernel installed.
Access the import and export commands by opening the command palette with Ctrl+Shift+P or Cmd+Shift+P and searching for "Hydrogen: Import Notebook" or "Hydrogen: Export Notebook". You can easily assign your own keybinding to these commands if you'd like.
Run Hydrogen: Import Notebook and select the desired notebook file in the file browser that opens. That's it! The file will be imported into a new Atom tab as a new file, using Cell Markers to delimit the individual code and markdown blocks. If you also wish to view your previous cell results, then make sure "Enable Import of Notebook Results" is checked in Hydrogen's package settings.
Note: In order for Hydrogen to automatically find the corresponding syntax highlighting package for a given programming language, your notebook file must contain the proper metadata and your grammar package of choice must be installed and active.
With text like the following, running "Hydrogen: Export Notebook" will export code and markdown cells to a Notebook file of your choosing.
# %%
print('Hello, world!')
# %% markdown
# A **Markdown** cell!Note: Exporting results is currently not supported.