One of our Project Managers was looking for this and was surprised it wasn’t possible.
You can group by Groups, but not by Items:
Yes this feature is missing. Makes the Gantt view pretty limited. You cannot Gantt several timeline columns on one Item and view it in any meaningful way.
The only way you can “group” by item that I have found is to use subitems with their own due dates. The Gantt view shifts the subitems slightly to the right of the main item, and groups them underneath the parent item name.
