You can customize the Outlook layout in many different ways. If you want to show the tasks list in the message window, please follow the steps below:
Step 1: In the message window, click the "View" tab from the Ribbon;
Step 2: Click "To-Do Bar" in the "Layout" section, then click "Tasks" from the list;
Step 3: The task list will appear in a separate column. The layout will change from the top of the picture below to the bottom part of the picture.