It would help if there was a node for:
Add JSON Lines option to the Convert to File (JSON) node (and to Extract from JSON node as well).
My use case:
For example, I have 2k items on input that has nested items that would be flattened up to 20k items and I need to save them in one file. Currently I can only save them in JSON file all at once. Thus the memory consumption is very big (my n8n instance almost died while processing it)
If there will be a JSON Lines support, then It would be much easier to handle. I could process each of the initial items separately and append their expanded values to the same file with no additional effort.
Also, JSON Lines files are usually used in the cases where there are a lot of data (e.g. 2M of entries). That is totally impossible to handle withing classic JSON file