With Ink support in Microsoft To Do you can add, complete, and delete tasks with the stroke of a pen. To Do recognizes the following actions in Ink:
Adding a task. Use your pen to enter a new task, then tap Add.
Completing a task. Use your pen to check it off, or draw a line through the task's name.
Delete a task. Use your pen to cross out the task name, or draw a line through a completed task.