In Satanism you are free to choose your partner with a legal sex age, bi, straight, gay it does not matter. As long you date the same race as you are.
The problem with transgender people is, they are programmed to not like their own gender, if one is born with a penis one is a male, if you have a vagina you are female. It´s quite rare that people have both (hermaphrodite), even then normaly only one off both is fully functioning, this means, the 100% one is there gender.
By engaging with such a person you have to cope with there programming. Like a female that looks more masculine wants to be called a men. I would not like this. You could try to explain that they should accept themself etc embrace there natural gender etc.
Your choice. As we should also try to help our partners, to be happy and improve in live.