Which brings me to the question whether I can edit the code in a text editor as well or I have to write it as shown in the animation. It would be really helpful if there was a shortcut to open the current (code) section in $EDITOR, kind of like Git and other tools do it.
The motivation behind this was to have some basic interaction with existing ipynb files on a remote server without having to run the jupyter server (and set up port forwarding etc.) It's worth noting that the `jupytext.vim plugin is most useful if you're actually not running `jupytext` within jupyter; If you are, you could just directly open the .py or .md files linked to any .ipynb in your editor.
I've used `jupytext.vim` to edit existing notebooks and then run them through `jupyter nbconvert --to notebook --execute`. It's also great for refactoring: moving code from a notebook files into a module, between notebooks, or to create a new notebook as a variation of an existing one.