Quick-Start guide to make Reorder list in UE5 is a hands-on Tutorial that shows you how to build reorderable UI lists in Unreal Engine 5 using UMG drag-and-drop.
https://dev.epicgames.com/community/learning/tutorials/YGVm/unreal-engine-quick-start-guide-to-make-reorder-list-in-ue5
appears that one of the blueprint diagrams is incomplete as the diagram does not match the text description. The diagram that should include the creation of the drag drop operation is missing that code.
Edit: On further inspection it appears that many of the diagrams are broken. As there are orphaned nodes on many of them I guess it could be a browser error.