this is an interesting app domain, and i believe very hard to get right in my opinion the best to-do app is orgmode i think if you need a web-app or your need

this is an interesting app domain, and i believe very hard to get right in my opinion the best to-do app is orgmode i think if you need a web-app or your needs exceed what orgmode offers, you are solving the wrong problem, and you probably need an issue tracker not a todo list a smart text file for personal is all what a todo list should be, anything more, you are crossing the boundaries of a todo list to an issue tracker