Creating new monsters by editing Monster Manual character sheets? (OGL)

Is there a way I can take a sheet from a Monster I got in the monster guide and edit it? I did so, but the token keeps trying to revert to the original monster sheet. For example, I dragged Twig Blight to my game, so I now have the sheet. I then renamed it Tree Blight and adjusted the stats and size. Then I readded Twig Blight. Only issue is I can only get it to create a Twig Blight Token with Twig Blight stats.

You'll need to (re)save the edited Token as the Default Token of the Tree Blight Character. This guide also might be helpful.

You need to delete the default token (open the sheet, click edit). It is still using the token associated with the Twig Blight.

You guys are great! Thanks a lot Loren S and Silvyre!