Mattias did an good job in the move towards a dockable IDE :-)
There exist a few problems with the form creation, that prevent proper operation of drag-dock. At best the IDE should not try to dock or otherwise place dockable windows.
A general problem is the update of the Caption of docked forms - their Caption is invisible! As a simple solution every change of the Caption of a docked control should be sent to its HostDockSite, so that it can update the DockCaption. An according UpdateDockCaption method should be added to TWinControl, which does nothing by default; TCustomForm instead updates its Caption, so that all (floathost...) docksites will always show the proper caption.