I am not able to get custom attribute in ID_TOKEN returned from AWS Cognito after successful user login.
Steps I tried :
1.Created user pool 2.C
I had the same trouble and your question came up when I was searching for a solution.
My custom attributes started to appear in ID token when I enabled profile scope in 'App client settings'. (available at: AWS console-> 'User pools'-> click your pool -> 'App client settings' -> 'Allowed OAuth Scopes')
(BTW: I was misled by this sentence from the documentation: "The openid scope returns all user attributes in the ID token that are readable by the client". In my case openid scope was not enough.)
Show Details, then Set attribute read and write permissions. Check the checkbox next to your attribute name under Readable Attributes.profile scope.