I'm a windows user, Camtasia for Windows has an option to run in software mode only "Integrated Graphics" Its under user preferences. I hope I'm not wasting your time as feature parity between Mac and Windows is not complete.
Mac is't that great anymore... Thanks Joe for your valuable time answering me. On my (new 16 inch) Macbook, this option seem lacking. Even when camtasia is running in the background and doing nothing, my radeon card is active.