Can heat pumps condensation line be run in wall?
Yes you can run them in the wall. Most mini splits installed today have the drains and the high and low pressure refrigerant lines run on the exterior of the home so this is very normal and has been industry standard for decades to run the condensate out an exterior wall or into a drain.
I would want to make sure the run was straight and you have the ability to clean it incase green gunkies grow in the line and creates plugs.