Understanding how central banks use their balance sheets: A critical categorisation

Stephen Cecchetti and Paul Tucker in this voxeu piece say that central banks use their balance sheets for multiple purpose. There is a need to list and specify these seperate purposes:

Since the Global Crisis, the size of central bank balance sheets has grown significantly. Traditional goals of price and financial stability are insufficient for assessing the success of modern central banking operations. This column introduces a new framework for categorising and understanding central bank balance sheet operations. Monetary policy decisions are separated from facilities for lender of last resort, market maker of last resort, providing selective credit, and ensuring emergency government financing. To maintain legitimacy and accountability, central banks should formally distinguish these operations by clearly setting out their purposes, objectives, and constraints.