There is not a direct snapshot feature of a VM, but there is a way to capture the state of a VM.
In Azure, managed disks & the snapshot feature are how you do this, but Managed Disks is not a part of Azure Stack.
In Azure Stack, you will need to go to the storage account that the VHD is located in. Next, Stop the VM and make sure that the VM's status shows 'stopped'. Last, copy the .VHD file to the same or another storage account. The copied .VHD file acts as a snapshot and can be used to create a new VM.