Mo. Rev. Stat. § 478.267
Notwithstanding the provisions of section 478.265, on and after January 2, 1979, in each county of the first class having a charter form of government and having a population of at least nine hundred thousand or more inhabitants, the judge of the probate division of the circuit court may appoint one person, who shall possess the same qualifications as a circuit judge, to act as commissioner of the probate division of the circuit court. The commissioner shall be appointed for a term of four years. The compensation of the commissioner shall be determined by the judge of the probate division of the circuit court, not to exceed the compensation of a circuit court judge, payable in the same manner and from the same source as the compensation of the judge who serves in the probate division of the circuit court. Subject to approval or rejection by the judge of the probate division, the commissioner shall have all the powers and duties of the judge. The judge shall by order of record reject or confirm all orders, judgments and decrees of the commissioner within the time the judge could set aside such orders, judgments or decrees had the same been made by him. If so confirmed, the orders, judgments and decrees shall have the same effect as if made by the judge on the date of their confirmation.
§ 478.267, RSMo