Where are Custom Attributes stored in AWS Cognito? - amazon-cognito

Question

I am attempting to stored detailed information about users in my AWS Cognito user pool. I can retrieve the standard attributes, such as name or username, just fine with user.attributes.phone_number, however attempting to to the same thing with user.attributes.custom:MyCustomAttribute simply yielded an error because of the colon. I have ensured that my custom attributes can be read from across all platforms.
I decided to inspect the return key to see where the custom attributes are supposed to be, to find this:
attributes: Object
email: (...)
email_verified: (...)
name: (...)
phone_number: (...)
phone_number_verified: (...)
sub: (...)
__ob__: Observer {value: {…}, dep: Dep, vmCount: 0}
get email: ƒ reactiveGetter()
set email: ƒ reactiveSetter(newVal)
get email_verified: ƒ reactiveGetter()
set email_verified: ƒ reactiveSetter(newVal)
get name: ƒ reactiveGetter()
set name: ƒ reactiveSetter(newVal)
get phone_number: ƒ reactiveGetter()
set phone_number: ƒ reactiveSetter(newVal)
get phone_number_verified: ƒ reactiveGetter()
set phone_number_verified: ƒ reactiveSetter(newVal)
get sub: ƒ reactiveGetter()
set sub: ƒ reactiveSetter(newVal)
__proto__: Object
Where/how am I supposed to be able to retrieve and edit my custom attributes and values? I've theorized that it may be in one of the tokens, but I don't have the experience to really act off of that. It seems that it may also not be showing because there is no data, but I need to know how to access them in the first place to change the data, leaving me in the same place.

Answer 1

Turns out that they are stored just fine, EXCEPT you cannot use dot notation to access them. Instead of:
user.attirbutes.custom:MyAttribute
You have to use:
user.attributes['custom:MyAttribute']
as per this GitHub discussion, where user annjawn says the above.