You need to either replace your current layout.json with the new one(if you haven't changed alot) or copy required_sub_manangeWeapon to your current one. You can technically also recreate it in the menu (Add option -> set type to sub -> sub -> press add and type required_sub_manangeWeapon)
Thanks, will add them in next version. Although you can actually add them by just pressing add option (Insert in edit mode) and setting action to spawnHorse, or edit layout.json directly(search for sub_horseSpawner)