I have created two Firestore databases inside my firebase project; one for development and the other for production (default). Unfortunately, I am unable to see the development database inside the firebase console but when I run the cloud command: gcloud firestore databases list it shows the list of all the databases, including the development db.
I have also created these databases in the same region. I specifically need to access the dev database in order to modify the security rules.
firebaser here
The ability to have multiple Firestore databases in a project is still in Preview at the moment, which means not all features may be available yet.
One of the features that is still in development is the ability to view the non-default databases in the Firebase console. It will be available before the feature leaves the Preview phase. It's actively being worked on, but they encountered some issues in the encoding of database IDs. For now, you can (only) view the non-default databases in the Google Cloud console.