Yes, you are right. I have overseen, it wasn't "local-lvm", but "local-zfs". I tested same install in VM and found it out.
Now, I (re)added ZFS "rpool/data" in the "Datacenter > Storage" and can use it again.
So, case is solved :)
I did, thanks. Now it exists only on older nodes.
How to recreate it now on the new node? Both GUI and pvesm add ask for Volume Group, which I supposedly, don't have on a node with single ZFS formatted disk.
I had a cluster with classical disk roles: one for Proxmox OS, another for VMs. It worked. Then I wanted to add a simple small node with single disk for DNS and Ngynx. I've installed Proxmox there, choosing to format disk as ZFS. It was installed and created "local" and "local-lvm" storage. Then...