[jsyolo]

You can save the data on disk and not worry about it.

Like in sqlite or something like json files?

[pclmulqdq]

Filesystems have a lot more flexibility than just storing JSON or databases. A notes app probably should just store markdown files with some links between each other, and a few small databases for indexes.

[sgtnoodle]

You could also store base64 encoded blobs in yaml, or implement a self-modifying bash script key-value store you call into from a shell. Those are the only other options before it's time to move everything over to into the cloud.