At this time, only one(1) environment is supported on Strapi Cloud. This should be used as a production environment.
While adding multiple environments is not currently on our roadmap, a *suggested potential workaround would be to create a second cloud project and utilize our data transfer feature, which streams your data from one Strapi instance to another Strapi instance.
*Please note that a workflow such as this would incur a charge per each cloud project.