We use a variety of custom item fields to manage key 'point in time' data on item records which is then sourced into various transaction columns on create. The overhead/possibility for error in manually managing these fields on both parent and child via csv (1x Parent Line + 5x Child Line VS just a Parent line) is a pain. I'm not too familiar with matrix item set up when implementing NS but always kind of assumed there'd be default mechanism for this kind of behaviour?