How can I add a custom emoji to the already existing emojis (ore replace one)

Hello I'm starting to play with the linux console apearance and I would like to customize the @ emoji, I know I can do it in many ways, I used

nano ~/.zshrc

and modified a few lines so i can replace it with

☠

(usual when going root in kali) or

㉿

(base in kali) my question here is to know if there is a way to add custom emojis to the emoji base software integrated in latest versions of linux if not can I create custom unicode emoji it's doesn't change anything but i'm on latest version of kali (you guessed)