Oracle 18c

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CREATE TABLE table_name (configuration CLOB CHECK (configuration IS JSON));
INSERT INTO table_name ( configuration )
VALUES ('{"sections":[{"active":true,"code":"page.about"},{"active":true,"code":"page.title"}]}');
1 rows affected

CREATE FUNCTION json_append_array(
  json  IN CLOB,
  path  IN VARCHAR2,
  value IN CLOB
) RETURN CLOB
IS
  j_obj JSON_OBJECT_T := JSON_OBJECT_T(json);
  j_arr JSON_ARRAY_T  := j_obj.get_Array(path);
BEGIN
  j_arr.append( JSON_OBJECT_T(value) );
  RETURN j_obj.to_Clob();
END;
/
UPDATE TABLE_NAME
SET configuration = JSON_APPEND_ARRAY(
                      configuration,
                      'sections',
                      '{"active":false,"code":"page.body"}'
                    );
1 rows affected

SELECT *
FROM   table_name;


CONFIGURATION


{"sections":[{"active":true,"code":"page.about"},{"active":true,"code":"page.title"},{"active":false,"code":"page.body"}]}