With Amplify version 5 in AppSync resolver works it:

"mydata": $util.toJson($context.identity.claims.get('custom:mydata')),

But with Amplify version 6 I not see my custom:mydata in:

 console.log(context.identity);

Output:

context: {
  identity: {
    claims: {
      origin_jti: '00449850...',
      sub: '31eed360-...',
      event_id: '5692337...',
      token_use: 'access',
      scope: 'aws.cognito.signin...',
      auth_time: 1714453811,
      iss: 'https://cognito-idp...',
      exp: 1714464611,
      iat: 1714453811,
      client_id: '976omhwqsu...',
      jti: '54u7d162...',
      username: 'myusername'
    },
    defaultAuthStrategy: 'ALLOW',
    groups: null,
    issuer: 'https://cognito-idp...',
    sourceIp: [ '120...' ],
    sub: '34end...',
    username: 'myusername'
  },
  ...
}

Any suggestion please?