Cassgender

Cassgender is a gender identity where one feels that their gender is unimportant or where one is indifferent to the idea of gender. Cassgender is different from a lack of gender, as a cassgender individual might have a gender but not feel that it's an important part of their identity.

A related term is cassflux, where the level of indifference fluctuates. Sometimes one might feel completely indifferent towards gender, but at other times gender might feel more important.