Section 23. The register of the respective courts of the probate and family court department may, with the approval of the chief justice of the probate and family court, appoint for a term of 3 years and may, with the approval of the chief justice, remove a first assistant register of probate. Before entering upon the performance of his duties, a first assistant register shall take the oath prescribed by the constitution. The appointments shall be as follows:
Essex, 1 first assistant register
Middlesex, 1 first assistant register
Norfolk, 1 first assistant register
Suffolk, 1 first assistant register
Worcester, 1 first assistant register.
Those persons serving as first assistant registers in the Barnstable, Berkshire, Bristol, Essex, Franklin, Hampden, Hampshire, Middlesex, Norfolk, Plymouth and Suffolk divisions of the probate and family court department shall become judicial case managers for a term of 3 years pursuant to section 23C in their respective courts.