When moving external dockable on screen, we can see only title or little image (in flat theme) of dockable content. Is possible to change this behavior to see entire dockable?
These images are created by a DockableMovingImageFactory. This factory is provided by the current DockTheme.
While it is possible to replace the factory, there exists no implementation for what you want. You would need to write one by yourself.
Btw. you can grab the window of the external Dockable at its upper edge to move it around. Then you would see the whole Dockable.