I too tried to add Class column to the credit card register.  I enabled class tracking.  I repaired Quickbooks Pro Destop 2018.   I looked for Class among the Available Columns to add.  It was not there.  I know one can get to it by Edit Transaction, just one more step that slows entry down.  I am surprised by QB Pro Desktop 2018.  I'm sorry.  QB Pro Desktop 2018' seems to be a step down from QB Pro 2014.  (Even that fat Search bar at the top of the Chart of Accounts is an annoyance.)  Please, would Intuit put the Class column back into the registers??