Peter--

Yes, Stage Manager is specifically designed to manage the pre-production (in your case, "isolated Test") environment. When Stage Manager is used to manage your pre-production and production infrastructure, it can be used to clone production workloads and make them available for pre-production work--patching testing, for example. Stage Manager suspends the virtual machines being cloned for the duration of that clone. If the clones being taken are "linked clones" that time can be very short--about a minute, in most cases. If the clones being taken are full clones, that time can be very long, depending on the size of your virtual machines. The product documentation should have more information on the differences between linked and full clones.