By default, your tasks are grouped into the buckets you use: To Do, In Progress, Completed, or any other bucket you've created. The planner also allows you to group tasks based on the due date, assignments, Priority, and more.
To change your task groups, click the "Group by Interval" button in the upper right corner of the Microsoft Planner interface.
Choose a different property to group your tasks, and they will be automatically rearranged. For example, if you choose "Priority," your tasks will be grouped into new Priority buckets.
You can drag and drop tasks between these buckets to change properties. Have you started testing and found some issues? No problem, group by "Progress" and drag the tasks you've tested back into the "In progress" column. Then group by "Assigned To" and drag the tasks into the buckets of the person who needs to resolve the issues or into the "Unassigned" bucket if someone can pick them up.
This process is much faster and more intuitive than laboriously opening each task and editing each field.