Hi manish verma,
Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.To add storage account from another subscription to the azure batch service, you need to have certain permissions and roles.
See that you have Owner or Contributor role in the Batch Account and check if its managed identity then ensure it has access to the storage account in the other subscription.
Add the role 'Storage Blob Data Contributor' or 'Storage Blob Data Owner' in the Add role assignment of IAM section. In the "Assign access to" dropdown, select either "Managed identity" or "User assigned managed identity" according to your batch service setup, search for and select your Batch account's managed identity, and then click "Save" to assign the roleNow go to the batch account, click on storage account then add storage account, the storage account will appear the add it.
Ensure that your Azure Batch service account and Storage account are in same region, or in supported region for cross-subscription resource linking.
For more information please refer Use managed identities in an Azure Batch account
If you have any further queries, please do let us know. If the answer is helpful, please click "Accept Answer" and "Upvote it."