With Ink support in Microsoft To Do you can add, complete and delete tasks with the stroke of a pen. To Do recognises the following actions in Ink:
Add a task: use your pen to enter a new task and then tap Add
Complete a task: use your pen to tick it off in the checkbox. Alternatively, you can also draw a line through the task name
Delete a task: use your pen to scribble out the task name. Alternatively, you can draw a line through a completed task.