On the Widget you’re dragging, go to the Graph view and next to Functions, click from the Override option the dropdown item called On Mouse Button Down. Then also click On Drag Detected. In On Mouse Button Down, from Mouse Event, drag and create a node called Detect Drag If Pressed. Choose the Left Mouse Button (or whatever button you use to drag and drop!). Now connect the output to the return out.
Now in On Drag Detected, you can drag from the Pointer Event and Get Screen Space Position on the mouse cursor. With a Deproject Screen to World node you could get World Space if you need it. The result can be Promoted to a Variable and then passed on later for whatever other needs you may have for it.
Does this give you the desired functionality you wanted?