In Blender, we have had drag and drop support for dragging content such as images onto objects, and 3d content into 3d views. However, we've always lacked the ability to drag the UI elements themselves.
This would be good to finally address.
This would mean we can get rid of these re-ordering buttons, which are slow because you can only move items one line at a time:
To support this nicely, we should use animation to make items move out of the way, and to let the current items follow the cursor. This makes the UI feel physical and dependable, and you won't get any sudden surprises when you let go of your drag action, and the UI elements suddenly re-order themselves.
This kind of thing has a few implications how we draw some UI elements.