I know the chess.com Game Wizard allows one to enter variations and sub-variations. I know Game Wizard allows one to paste in PGN that has variations and sub-variations.

But I do not know how to replay such varations and sub-variations from the inserted diagram.

I would like that feature. It would let people post well-annotated games.

Well you can access the variations and sub-variations through the move list. I'm not sure I really know what feature you want added.

yea that would be pretty cool

I see page http://www.kenilworthchessclub.org/articles/opening/isolani/isolani-best-B.htm has a game player with a "step into variations" button.