The elevator trim assignment has a repeat box that controls the rate that the tab will move with a continuous push of the button. Adjusting the rate slider may make the trim tab less sensitive.
Trim system
The elevator trim tab is designed to remove control pressure during flight. It is not a autopilot. It is normal for the aircraft to climb or descend when the pilot releases the stick even in a correctly trimmed aircraft. You have to fly the aircraft at all times. The trim is to prevent pilot fatigue in small aircraft but was not even included in the first aircrafts(the Jenny doesn't have a trim system). In large aircraft it's more important because the pilot may not be able to overcome the force of a out of trim condition. It's like if you take your hands off of the steering wheel of a car on the highway, it's trimmed to go straight but it will only go straight for a short distance without small corrections. Same thing with an aircraft, you have to fly it with small corrections unless it's on autopilot. 🙂