Transgender refers to how people "identify".
TransɛҳuąƖ refers to gender reassignment surgery.
The first, while disgusting, is not a mortally sinful action unless the purpose of your dressing up is to cause someone else to commit mortal sin.
That's not how God sees it: "A woman shall not be clothed with man's apparel, neither shall a man use woman's apparel: for he that doeth these things is abominable before God." Deut. 22:5
Sounds like a grave sin to me, at least according to how Lad defined "grave sin" (exterior forum)
The second could be mortally sinful depending upon the disposition.
I don't see how it
isn't mortally sinful. It's a grave act against human nature. We could question the
disposition of one who commits the act of sodomy and find ourselves in the same position as the heretics in the Novus Ordo who dismiss it because God "made them that way". Ridiculous.
Both transgenderism and transsɛҳuąƖism are both mortally sinful since they defile human nature.