"trans" as an adjective functions similarly to "super", as an indeclinable adjective. Indeclinable means that it is not inflected like most of the adjectives in German:
It therefore means "a super person" (not "a super person") and this also applies to "trans" as an adjective.
Older spellings such as "transperson" are no longer used. The reason for this is the analogy with other characteristics attributed to people, such as "the big person". No one would talk about "big person". And for good reason!
Attaching qualities to nouns in this way has a very different effect. A "super man" is also really something quite different from a "superman" - the stress is also on a different syllable and instead of a description as "great"="super", superpowers are attributed to this man.
The use of trans (or also trans*) can thus be imagined as a short form of "transgender".
Where trans- can and should continue to be used as a prefix (i.e. tacked on to the front of another word) are the moments when trans is relevant not as a quality of a person but as a subject matter: trans hostility, trans rights, etc. The hostility is not trans, but is directed against transness. Rights are not trans, but are for trans people. Hostility would not be framed as "human hostility" either.
So it is a great step that trans is in the Duden as a simple indeclinable adjective, because it makes it possible to recognise trans people for the quality of being trans without denying them anything else: A trans woman is thus first and foremost a woman.
More exciting articles: