Drag'n'drop for GridPro edit Column

I enable drag’n’drop on one grid to another grid. This works perfectly: when I grab a row in the source grid and drag it over, the event handler methods for drag-start on the source component and handle-drop on the target component are called. So far all is well. However, if the source grid(Pro) contain an editColumn with a textfield as custom edit component, a drag-start event is no longer generated and the whole mechanism no longer works. I tried to make the TextField

DragSource<TextField> dragSource = DragSource.create(this.editColumTextField);

and the Column

DragSource<Grid.Column<GridDto>> dragSource2 = DragSource.create(column);

draggable via DragSource, but neither works.

How do I make an editColumn in the grid draggable?