Hello Nicolas,
There is no such feature right now :-/ The best way to save your notes is to copy and paste them somewhere else and then recreate them.
You can still play with CouchDB if you host your Cozy yourself.
Sorry for the inconvenience, we hope that you will be able to reinstall your Cozy. I'd also like to apologize for the lack of support from our side regarding your issues, I've seen an email without noticing it was not someone from our team. Let us know if anything goes wrong again and we will carefully help you.
Cheers,
Joseph.