How to create a Reaction.
In the project window, right-click and select Create > Modular Melee Combat Framework > Reaction> left-click.

Data Type
StaggerStateEnum (enum)
If the target is attacked while the current reaction is still active, then the new reaction is determined by the selected state.
IgnoreHit - ignores the hit completely.
DamageOnly - doesn't play the ReactionAnimation, but applies damage and plays the hit/audio effect for this target.
FullReaction - plays the ReactionAnimation as well as applies damage and plays the hit/audio effect for this target.
Variables
ReactAnimation (AnimationClip) - the animation that plays for this reaction.
AnimationPlaybackSpeed (float) - animation speed for ReactAnimation.
ExitTime (float) - determines how long the current reaction is considered active. If the target is attacked while the reaction is still active and has not reached ExitTime, StaggerState determines how the new reaction is handled.
HitEffect (GameObject) - the effect that is played on impact, this can be a ParticleSystem or VisualEffect, as long as it is set to play on awake, the effect is disabled after HitEffectDuration.
HitEffectPos (GameObject) - defines the position and rotation for HitEffect, if left empty it will inherit its position from the point of impact (set via code) , rotation will be zero and parent will be set by Object Pool Manager.
HitEffectDuration (float) - duration for HitEffect.