For those that use only Flat Rate or Hourly Rate or Units, you can creat new templates and uncheck boxes in the Content field (to avoid seeing Qty and Rate for instance and only see Amount) and you can change the name of the field (QTY to HRS for instance) which is good - but for those of us who use more than one type of billing on one invoice this doesn't work.  I use Hours for some services and other services are Flat Rate and need to be on the same invoice.  The workaround doesn't work. 

In the meantime, I just made separate templates for each type of invoice,  for those that use only one type of rate (Hourly, Flat Rate or Units).