Very much appreciate the idea of building your own tools. That said, I have some lightweight coding chops, but I'm no developer.
Drafts.app, (my goto app for notes and tasks) is probably the closest I'll get to building something for myself, thanks to the way it lends itself to being extended by Javascript actions/plugins. Beyond that, I'm fond of smaller tools that match my sensibilities and don't try to be everything for everyone.
Also, from Linus’s post, the relationship between notes and tasks that he posits makes so much sense, the fact that a system like his needs to be able to flag a note as an actionable item. Same vibe here.