I want a to-do list app that syncs from a json file (or other human-readable data format), so that I can view and modify the file (via a CLI like jq) from my computer too, and it would still reflect on my phone when it syncs.
Does this exist? Preferably it uses a format simple enough that makes it possible / easy to modify it via jq.
Not exactly what you asked for but Joplin files are markdown. The app itself (very cross platform) renders them in a nice format. https://joplinapp.org/
A surprising number of people will tell you that the reason they prefer the closed-source Obsidian to Joplin is that Joplin doesn’t use Markdown files as its backend format to store its notes, but rather a database file. (They are formatted with Markdown, though.) I think the concerns they often express around lock-in are overblown, but this may mean it’s not what OP is looking for. I agree that the Joplin app is pretty nice, though more polished and featureful on desktop.
You can literally export all your notes in 2 clicks. You right-click on your notebook, hover over the export menu and select Markdown. Choose a location and Joplin will create a folder with all your notes in Markdown format inside.
Oh, I’m well aware. But the criticism I’m describing is that Joplin doesn’t write and read the notes as plain .md files on-disk as its storage backend. As I said, the lock-in component to the criticism is overblown (due to, yes, the ease of export), but people also tout the Obsidian approach to storage as allowing more flexibility to also access and edit your notes collection outside of the application, not to mention the flexibility to roll your own two-way syncing solution to other devices that don’t run Joplin, edit notes there and have changed synced back to notes in the application. I use and enjoy Joplin, and wish they would add something like that.
I brought this up because of what OP mentioned re: “view and modify” notes in something like
jq. I’m sure they’d want their external changes synced back to their notes.