A first version is implemented for listing presentations. However, there is basically
no test for this.

Here is an example:

GLMBasicExamples>>listDragAndDrop
    "self new listDragAndDrop openOn: (1 to: 5) asOrderedCollection"
    | browser |
    browser := GLMTabulator new.
    browser column: #source; column: #target.
    browser transmit to: #source; andShow: [:a | 
        a list 
            title: 'Source';
            display: (1 to: 10);
            allowItemDrag: [:item :list | true ];
            transformDraggedItem: [:item :list | item + 100 ]
            ].
    browser transmit to: #target; andShow: [:a |  
        a list
            title: 'Target'; 
            display: [:collection | collection ];
            allowDropOnItem: [:draggedObject :targetItem :list | draggedObject isNumber ];
            dropOnItem: [:draggedObject :targetItem :list | 
                list entity addLast: (targetItem + draggedObject).
                list update.
                true ]
            ].
    ^ browser

NIce to see such quick action, Doru! 

The interface for dropping might become a bit more complex. Let's consider a tree view.
The drop can be either on an element of the tree (supported), or in the free area below
it. But it can also be between elements (to add at a specific position in the tree)
or even at a certain level of the tree (to add as a child)

Indeed, these are all actions that should be supported. However, I am already happy
that I discovered how to do this with Morphic :)

We would need more help from the widgets to handle the in-between dropping. Right now,
there does not seem to be a way to do this in Morphic, probably because there is no
space in between the rows. Dropping below the list seems to be possible.

Not for 4.7