When you set up a birthday input field on the Shopify member registration screen, there is a way to save the value using Customer notes, but this is a way to set the value in Customer tags. This is used when you need to determine the birth month by tag for a points app, etc.
How to set a birthday input field on the account creation screen and set the entered value as a tag
[How to set it] Add the code to the main-register.liquid form (basically, only one customer[tags] can be registered, but multiple values can be set by connecting the values with a comma (,))
