The OP is in EASA land, where you log IFR everytime you fly according to the IFR rules, being IMC or VMC does not matter.
Is there a seperate entry in a commercial pilot's logbook for IFR? Genuine question. Anyone with a plain vanilla PPL can fly IFR as long as it's within the limits of their license; although obviously they can't do any real or simulated instrument flying unless under instruction. There's no actual column for IFR flight though in a PPL logbook except to put it in the 'comments' column.