To obtain an Amazon Germany GmbH residency certificate for 2023 with an inactive seller account, you'll likely need to navigate Amazon's support structure outside of the seller support's limited options. Here's a strategy to consider:

1. **Amazon Seller Forums**: First, try the Amazon Seller Forums for advice from other sellers who might have faced similar issues. Sometimes, experienced sellers share specific contacts or indirect methods to reach different departments within Amazon.

2. **General Amazon Support**: Since your issue transcends typical seller support topics, contacting Amazon's general customer support might provide a pathway. Explain your situation and clearly state that you're seeking assistance regarding tax documentation from Amazon Germany GmbH. They might redirect you to the appropriate department or provide an alternative contact method.

3. **Tax and Legal Advice**: Consulting with a tax advisor or legal professional experienced in e-commerce might offer a solution. These professionals often have direct contacts within large corporations like Amazon or know the legal pathways to compel Amazon to provide the necessary documentation.

4. **Amazon’s Tax Central**: For active sellers, Amazon’s Tax Central is the go-to place for tax documents. Although your account is inactive, try accessing Tax Central if you can log in to your Seller Central account. If access is possible, you might find the residency certificate or a way to request it there.

5. **LinkedIn and Professional Networks**: Leveraging LinkedIn to connect with Amazon employees in the tax, legal, or seller support departments might be a long shot but is worth considering. A polite inquiry explaining your situation could lead to helpful advice or direct assistance.

6. **Reactivation of Seller Account**: If other methods fail, consider attempting to resolve the suspension of your seller account as a pathway to regain full access to seller support. Once reinstated, you could directly request the residency certificate through the proper channels.

Given the complexity of navigating Amazon's support structure, persistence and exploring multiple avenues simultaneously might be necessary. Keep detailed records of all communications for reference in further discussions or as evidence if legal action becomes necessary to obtain the document.