Wat exactly do you mean? By default with an LVM installation you sould have both. A "local" LV which stored your root filesystem and a "local-lvm" LVM-Thin pool which stores your block devices for you guests. If you want to move capacity from "local" to "local-lvm" you could lower the size of your "local" LV and extend the size of your LVM-Thin pool. But that isn't that easy and can only be done using the CLI using LVM commands.