Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Collisions
HAIR_COLLIDER_COLLISIONSParameter: Friction
HAIR_COLLIDER_FRICTIONParameter: Bounce
HAIR_COLLIDER_BOUNCEParameter: Forces
HAIR_COLLIDER_FORCESParameter: Radius
HAIR_COLLIDER_FORCES_OBJECTS_RADIUSParameter: Strength
HAIR_COLLIDER_FORCE_STRENGTHParameter: Max Strength
HAIR_COLLIDER_FORCES_OBJECTS_MAXSTRENGTHParameter: Falloff
HAIR_COLLIDER_FORCES_OBJECTS_FALLOFFParameter: Custom
HAIR_COLLIDER_FORCES_OBJECTS_FALLOFF_SPLINEParameter: Restrict
HAIR_COLLIDER_LINKParameter: Strength
HAIR_COLLIDER_FORCE_STRENGTH_LINK