I just learned they've built the API for this, but looks like CloudFormation does not support it yet.

https://docs.aws.amazon.com/directoryservicedata/latest/DirectoryServiceDataAPIReference/Welcome.html

Consider using the AwsCustomResource CDK construct to invoke the Amazon API from your CDK application. https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.custom_resources.AwsCustomResource.html