Instead of triggering the actions by the direction of the thumb stick, you could set a direction variable on the sprite object. Then the event to trigger the action would be the value of the variable. Since a thumb stick doesn't directly spring back 0 but could over shoot it a little, you would want the axis greater/less than an acceptable value so the player doesn't accidentally windup walking the wrong direction. Also you would have to set up another event specifically for setting the variable back to 0.
Note, using a value of 0 with a thumb stick or joystick always has the possibility of causing adverse affects when the player releases it. If the player pulls the stick to it's farthest right position and releases it for example, it could spring back to the left a couple degrees causing the system to reset the value to the opposite of what the player wants.