The Library Manager window was made modal and can be set to remain open, rather than be dockable so that it can be positioned off of the application main windows. To make such a dialog as this with all its contents dockable, would eat a large area away from the 'working' window when docked. The manager tool is such a tool that is likely to be used occasionally.
Surely the window would need to be rearranged a bit but having it dockable gives user more flexibility to organize his workspace the way he sees fit. Thanks for filing a suggestion.