Azure Cosmos DB has numerous preview features for which you can request access. Here are the methods for requesting access to these preview features.

1. Navigate to the Preview Features section of your Azure subscription.
2. Under Type, choose “Microsoft.DocumentDB”.
3. Click on the feature you want to see in the list of available preview features.
4. To participate in the preview, click the Register button located at the top of the page.

Ref: Steps to register for a preview feature