Assuming its a TP run and you only have hand baggage, 1 hour is very achievable. MAN T3 is very small, and quite easy to navigate.
Sometimes the OLCI does not specify priority lanes for security, so if queue's are bad you may wish to go and get the check in staff to print you a new BP or add a priority lane sticker on your BP. Even then queue's at T3 MAN are rarely more than 5-10 mins.