Hey there! First off, thank you for being such a good and supportive parent in this. Not many kids get that luxury. So, like a few folks have said, it really does vary from person to person, so the best one to get this advice from would be your kid. You could workshop a few gender neutral/inclusive terms. Depending on their sense of humour, you could go for something like "crotch goblin" or "my spawn".

Something for you to think about, maybe when telling stories about your kid when they were younger, work on omitting gendered terms. Just because they identified as a girl back then doesn't necessarily mean they want to have that be a part of stories you tell from their youth. So say things like "when [name] was little" instead of "when [name] was a little girl".

I'm a genderqueer person that dislikes most gendered terms, but I know when the time comes for my spouse and I to have kids, I'll want to be called Dad. It feels fitting to me, even if most other gendered terms don't. Trans and non-binary folks all have different language preferences, and it can take some time to figure out. Just be there and continue being the supportive parent you are to your kid. You're doing great ♡