It is not necessary to check the manual transmission fluid level. A transmission fluid leak is the only reason for fluid loss. If a leak occurs, take the vehicle to a dealer/retailer for service. Have it repaired as soon as possible. You may also have the fluid level checked by your dealer/retailer when the oil is changed. See Recommended Fluids and Lubricants for the proper fluid to use.
Chevrolet Cobalt Owners Manual. Shifting Into Park (Automatic Transmission)
WARNING:
It can be dangerous to get out of the vehicle if the
shift lever is not fully in P (Park) with the parking
brake firmly set. The vehicle can roll. If you have
left the engine running, the vehicle can move
suddenly. You or others could be injured. To be
sure the vehicle will not move, ...