Make it auto-generated, choose an overall supernet then define the subnet each store will have. It will auto-generate however you can go into each of the networks and override the subnet. The caveat is that it has to be the same subnet mask as what you defined from the VLAN templates and has to be within the supernet scope. We do push the override back to the cloud so we do not auto-generate an overlapping subnet.
Is this what your looking for?