I already know the answer on the subject, but I would love to hear everybody's opinion on the matter.

So while at work, I prosed the question to my new manager, of seeing if I can "use my preferred name" Kate. So as per justification on my end, I had mentioned that others in the store are using names not thereof of their proper legal name on documents, even as he himself uses a name not thereof his legal name. He goes by Dan, instead of the full name of Daniel.
Two females that work under different names, that are completely different from their birth names (lets just give a formal example but not give their real name or their alias, but as example of a name such as Theresa, but would be preferred to Bea) as well as the assistant manager goes by Ken instead of Kenneth.
Now this is the kicker, even with this in mind, he still refuses to let me on board with using my "preferred" name. He is not opening his eyes to such a manner of such, and to which I hope it is his words or an interpretation of words coming from our district manager, and not my district manager himself saying it, but in an inclusion of having as such "it has to be legally changed to go by the name" the words expressed as they are said. And an inclusive "it is not discrimination, unless you are fully transitioned" those exact words stated in discussion.. But what exactly entails a "full transition"?
So I am excluded in this whole use of preferred name simply because it does not fit a gender not thereof its own... Newsflash to those that believe otherwise: Males do have such names as Ashley and Hillary, legally as I have met some. But this is dealing with not so legally changed preferred names, so this newsflash to those is not pertaining to this subject at hand.

Also to boot under their policy 4.10 on their nondiscrimination clause justifies there will be no discrimination as per gender identity.
Which I have clearly stated as well toward this.

Note: I will be getting in contact with HR tomorrow.

Discussion topics:
1) Does this sound like discrimination on multiple levels?
2) What exactly is fully transitioned?
3) Legalities under pretense of being able to use preferred names.

Kate <3

Yes, that is discrimination. They have no right to judge whether you are "fully transitioned", or to define that term for you. I suspect your manager is ignorant about trans issues and has outdated notions of what it means to transition.

I don't know what the laws are like in your area. If you're in the U.S., the EEOC will take up discrimination complaints based on gender identity. I would start by getting in touch with whatever local LGBT support organizations exist (nearly everywhere has them). Also, write down every conversation you have with your employer and when it happened. The next step would be to talk to the human resources group at your work and tell them you consider it discrimination that because you are trans, you are not being permitted to use your preferred name.