I think Biden had said long ago that he wouldn't do that no matter what; in this political environment it probably wouldn't happen anyway.
By the way, appellate courts sit right below the U.S. Supreme Court and there are currently 13 of them.
Some legal experts argue there should be one supreme court justice per appellate court, because that was the ratio when the appellate court system was first established in 1891 -- nine supreme court justices and nine appellate courts.