[SerializeField] private AnimancerComponent _Animancer;
[SerializeField] private LinearMixerTransition _Mixer;

private MixerParameterTweenFloat _MixerTween;

private void Awake()
{
    // Play creates the LinearMixerState from the transition.
    _Animancer.Play(_Mixer);

    // Now that the state exists, we can create a tween for it.
    _MixerTween = new MixerParameterTweenFloat(_Mixer.State);

    // Start tweening the parameter towards 0.5 over a period of 0.25 seconds.
    _MixerTween.Start(0.5f, 0.25f);
}