The following shows how to import a AppStack to another site. There maybe a scenario where you have another site such as DR that has its own App Volumes server and you need to import existing AppStacks over. There a good blog here on the different scenarios. It is possible to have multi site configuration depending on your SQL version here.

First connect to the source ESXi host and the destination ESXi host using WinSCP. Browse to the relevent datastore \vmfs\datastore name\cloudvolumes\app copy the required AppStack vmdk files to the destination datastore. This will bloat the disk so make sure you have available storage on the destination side

On the destination App Volumes server login to App Volumes - Volumes - Import AppStacks.

Browse to the new storage location path and select Import - Import volumes immediately

Once complete you will see the AppStacks available to assign

Notice the AppStacks are imported with no assignment, you will need to assign these again manually. If you want to share the database look at a multi site configuration here