StackSetsのスタックに既存リソースを追記して、その状態からStackSetsを実行してみる

AWSTemplateFormatVersion: 2010-09-09
Description: Import test
Resources:
  ImportedBucket1:
    Type: AWS::S3::Bucket
    Properties:
      PublicAccessBlockConfiguration:
        BlockPublicAcls: True
        BlockPublicPolicy: True
        IgnorePublicAcls: True
        RestrictPublicBuckets: True
      BucketEncryption:
        ServerSideEncryptionConfiguration:
          - ServerSideEncryptionByDefault:
              SSEAlgorithm: AES256