Can I use subtasks with Microsoft To-Do on Windows and Web?
Yes, you can use Steps to break your larger tasks down in to smaller, more actionable pieces. To add a step, just click the task to open detail view and then click + Add step and begin typing your next step. Once you've finished, just hit enter. To help keep you on track, a counter beneath each task's name displays the total number of steps the to-do contains and how many have been completed so far.
Like a task, a step can be completed by clicking the circle to the left of the step's name. To delete a step, just click the x to the right of the step's name.