Here’s a guide: Resizing LVM-on-LUKS - ArchWiki
It’s all generic linux ops, only lvm structure is qubes-specific. Stop before resizing logical volume and consider which logical volumes you want to extend and how much - dom0-related ones, vm-pool, or do something else entirely.
Technically you don’t even need to change the partitioning scheme on your disk, you can just reuse the old partition by encrypting it with the same passphrase and then extending your lvm infrastructure over it however you want. Here’s how: Add new device to the default `vm-pool`