AND created(I assume)the characters Samantha and Darrin.But who created Endora,Maurice,Gladys and Abner Kravitz,Larry Tate ,Louise Tate,Dr.Bombay,Aunt Clara,Uncle Arthur,Serena,Tabitha,and later on,Esmeralda,and Adam?

Your guess is as good as mine - but you may want to try writing to Herbie J. Pilato, the writer of Bewitched Forever. He interviewed cast, crew, producers, writers, directors, relatives and guest stars dating back to 1989 (the first edition of the book was published in 1992). He's on Facebook, has a blog, and here is his email according to his website: hjpilato@yahoo.com - so there you go!!

(Here is the link to his blog: http://herbiejpilato.blogspot.com/ - enjoy!!)