Hi,
You need to enable Editable Grid control for the Order Entity.
Here are the steps to enable Editable Grid control:
- Go to Advanced Settings -> Customizations -> Customize this System.
- Expand the Entities -> Order.
- On the Controls tab, click on Add Control.

- Select Editable Grid from the list and click on Add.

- Click on the radio button under Web for Editable Grid Control to enable it and click Save on the ribbon.

Refresh your browser, you could see Group By is added in the Order Views.

Let me know if you need further clarification.
Best,
Wahaj
(if it helps, please mark this answer as verified)