Over the last few years, I have been tried a variety of to-do list apps over the last few years, including Todoist, TickTick, Microsoft To-do, Wunderlist, and others.
One thing that I have learned is that everyone has a unique mental model, there is no one-size-fits-all to-do approach. The perfect to-do app is the one that constantly evolve to adapt its user’s mental model.
That's why I build my own to-do app using Coda, a programmable doc tool, that adapts to my needs and mental model.
As I previously stated, my approach might or might not fit your mental model, but it can serve as a starting point, and with Coda's extensibility, you can build your own to-do app on top of mine.