Set a Default Storage Location

I have 1 VMM
which contains 1 Cluster
which contains 2 Hosts
I am using ClusterStorage on the hosts

When I create or convert a VM, the possible paths are:
C:\ (default)
C:\ClusterStorage\Volume1

The option to "Add this path to the list" is grayed out

I want to add C:\ClusterStorage\Volume1\VMs to the possible paths AND make it the deault path.

How do I do that?

Thank you
James