Is it supported to copy a managed disk snapshot to a separate region?
You can't create snapshot to different region.
But you can create snapshot to the same region, then copy the snapshot as VHD to a storage account in different region, then create a managed disk from a VHD.
Sample script:
subscriptionId=dd80b94e-0463-4a65-8d04-c94f403879dc
resourceGroupName=myResourceGroupName
snapshotName=mySnapshotName
sasExpiryDuration=3600
storageAccountName=mystorageaccountname
storageContainerName=mystoragecontainername
storageAccountKey=mystorageaccountkey
destinationVHDFileName=myvhdfilename
az account set --subscription $subscriptionId
sas=$(az snapshot grant-access --resource-group $resourceGroupName --name $snapshotName --duration-in-seconds $sasExpiryDuration --query [accessSas] -o tsv)
az storage blob copy start --destination-blob $destinationVHDFileName --destination-container $storageContainerName --account-name $storageAccountName --account-key $storageAccountKey --source-uri $sas
More information about export/copy managed snapshots as VHD to a storage account in different region, please refer to this link.
More information about create a managed disk from a VHD, please refer to this link.