Hi TeaBiscuit,
From your posts, you seem to be a nice person, so I'm guessing your name refers to Nice biscuits which are designed to be dunked in tea?!
On the theme of Rebel8's link above, if you believe that God (or any other deity) designed or created animals, then there are several species whose biology and behaviour patterns could indicate that He is fine with transgender.
Or if you believe that God started life and left it to evolve, then we can at least say that He hasn't so far chosen to make these species extinct, which he could do if he didn't approve of sex changes.
The Clownfish (remember 'Finding Nemo') is an example..
It is a hermaphrodite which means that individuals are capable of changing their gender at some point in their life.
This does not imply that they are 'transgender' in terms of their psychology or that they suffer from the feeling of being born in the wrong body. They change merely for species survival reasons.
All babies are born male. They live in groups made up of all males and one female, and there is a hierarchy in each group with the female fish generally being the largest and most dominant fish in the group.
The 'alpha male' will be the only one to breed with the female and both take turns in guarding the eggs. If the female dies, this dominate male begins to gain weight and will change sex to become the female of the group.
This is just one example of many similar occurrences in nature, and as I said, although its not a parallel to human transgender issues, for Christians it could be used to show that the concept of sex change at least in the animal kingdom is presumably not abhorrent to God.
But for the Watchtower, it seems that anything and everything which is even remotely or distantly connected to 'sex' is automatically abhorrent and sinful.