In my three years of having FeralHeart, the only character I remember seeing that wasn't cisgender (male or female) was genderfluid, but mainly used male pronouns. (He, him, his, and sometimes they/them.)
Like you have a Finni character on FH, I have a Grell character, who is transgender. I suppose that could count as what you're talking about.
But other than all of that, I've never seen any agenders, bigenders, other transgenders, etc. etc.