easeInOutBack property
An easing function that combines the properties of easeInBack and easeOutBack, starting with a slight overshoot, building up momentum gradually, and then returning to the final value with a faster deceleration than easeInBack.
This is a good choice for animations that should have a natural and organic feel throughout the entire animation, with a focus on both acceleration and deceleration.
Implementation
static EaseFunction easeInOutBack = Curves.easeInOutBack.transform;