I’d bet a tablet woven belt made by hand that there’s no documentation for transgender Vikings.
Gender roles in Norse literature were very different than what they are today (or 50 years ago), what with shield-maidens and such, and Odin takes on a female form in Lokasenna.
I know it isn’t the same, but the Viking Answer Lady has an article on homosexuality in Viking culture which may be of interest. If anything, you could consult some of her sources.
Good luck to you!
ND: Initially reblogged with the personal account. Silly me. 😀