Hello @Salander He ,
Welcome to the Microsoft Q&A platform.
Unfortunately, it is not possible to access an external storage account in HDInsight cluster without access key.
Yes, you can add additional storage account after the cluster has been created.
While creating an HDInsight cluster, you specify the Azure Storage account you want to associate with it. Also, you can add additional storage accounts from the same Azure subscription or different Azure subscriptions during the creation process or after a cluster has been created.
For more details, refer to Add additional storage accounts to HDInsight.
Hope this helps. Do let us know if you any further queries.
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