Can I add a spouse to my Apple savings account

No, currently Apple Savings account is an individual account. If the Apple Card account is co-owned, each co-owner may open an individual Apple Savings account.

I can’t believe this functionality hasn’t been added yet.

i have to xfer money out to joint account every so often due to this. Inconvenient.

I understand and appreciate your desire to setup an emergency fund and share it with your family. Unfortunately, HYSA are intended to accumulate wealth and generally have limited conveniences like bill pay, multiple owners or sharing.

This would be great if it were possible to share the savings account with family members. It would make a good shared emergency fund.