This is how I originally learned to manage my tasks as well. It's a good system.

. . notepad.exe or vi if you have linux. I spent a long time writing software the manages todos (https://oggflow.com) (among other things), but nothing beats notepad.exe (or any plain text file editor.) I use the following notations:

- this is an unfinished task (due date: Apr 1 2018)
    - this is a subtask (note: don't forget to whatever)
o this is a task I'm currently working
v this is a task I've finished

Nothing beats this for me. I sometimes even do this on paper instead of the computer.