The hash_maps table is actually a view consisting of the four columns having the same names of the dict_obj_info table, as shown here:

CREATE VIEW hash_maps AS
  SELECT id, version, state, fq_name
  FROM dict_obj_info
  WHERE type=24;  # Hash map; defined in dict_obj_types

See the description of dict_obj_info for more information.

The hash_maps table was added in NDB 8.0.29.