I believe there should be limits to what minors should be allowed to do. When an adult becomes sexually attracted to a minor, the society frowns at it because it is believed that the minor does not have the mental capacity to give consent. Gender transition is something an individual needs to think through before proceeding with it. Children undergo different growth processes and at each stage, their taste, personality and how they see life might be affected. At that point, any wrong decision made may live with them for a lifetime.
I can recall how as a child I wished to be so many things which I ended up not being. Right now as an adult, I wouldn't consider being any of those things I wished to be as a child. If I am in the position to make and implement this law, I will criminalize gender transition surgery on all minors with or without the consent of their parents. They should be adults first and then we can be sure they actually consented to it themselves.
This is a complicated issue. One dimension is the medical safety of the treatment, the effectiveness, and the proper prescription of it. In other words, is this the right thing to do for somebody's health. The State regulates drugs and medical procedures all of the time along these lines, and the answer is a
scientific one--but science isn't always fully settled, and I believe there is a lot we still don't know about human gender in a very specific physiological way.
The next dimension is parental consent. Laws around children are nuanced and never very exact because the status of a child is partially that of a full legal person and partially that of property of the parents--a child is not afforded the same rights as an adult, but they still have some rights as a person. The middle ground here is cause for lots of laws to be very vague, and often lead to bad outcomes
no matter what they say because no single rule can handle every situation.
Both of these things together basically amount to: no matter what law you put on the books, it's probably going to be wrong.
The third--and unwelcome--dimension for this issue is the vile bigotry you see displayed by some posters on this thread. Some people, it seems, feel that all gay people must die, and they seem to feel very strongly about that. And they all vote Republican in hopes that they can enforce their feelings with the law

.
Hence this is a complicated issue to begin with, and then bigoted emotion enters into the discussion and blows away any chance of there being anything close to rational in many jurisdictions.
My own view here is to do what Americans have always done in this situation and
make the default position to be freedom. In other words, if we aren't sure what law will work, then let individuals decide.