DragDropOperation is removed when pressing esc button. but this is skipping OnDragCancelled so it can disrupt user's UMG drag operation logic.
1) Create a new widget blueprint(A, B)
2) Create drag setup(Detect drag at OnMousePreview, CreateDragandDropOperation at OnDragDetected) in B
3) Place B on A
4) Make persistent level blueprint to create and add the A widget into viewport
5) Run in PIE
6) Press esc while dragging the widget
Here is sample project [Link Removed]
Head over to the existing AnswerHub thread and let us know what's up.