The visualforce page you reference in the CMDB is not customizable, so I am not aware of a way to expose a custom object in the details section.
Can you elaborate more on your use case? The details tab exposes all major items (ex. incidents, service request, changes, etc...). There may be another option here. Thanks
Please note that a separate license is required from Salesforce to create custom objects, that option is not included in the Remedyforce license.