Jan 6-2020.   Another way to do a class entry while working in a register:  Press <Alt+S> keys.  That opens the Edit Transaction window right away with the class column.  You are not alone.  Many of us have this same question.  Intuit support keeps telling us to check back for this feature, class column in the register, to be added.  I don't think that's going to happen any time soon.  It's been over a year since your query was posted.