How to add multiple product group under service usage?

Summary:

We want to define product groups for multiple Customers and want to use them as Covered levels(Product Groups) in the Subscription management system. 

Content (required):

We want to know how we can add multiple product groups under the "Service" usage definition. Currently, we are getting the attached error while trying to add a second product group to usage.

If this is not achievable, please let us know if we can add custom Product group usage for Subscription Management Products to achieve the same.

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Code Snippet (add any code snippets that support your topic, if applicable):