Btrfs question for Fedora 33 beta. How can I add nocow to /var

I am looking to some performance considerations for the /etc/fstab btrs default config generated by anaconda. It appears to have created a subvol for root (root00) and for home (home00). I would like to put in /opt with it's subvol, and to migrate the /var to a subvol where I can specify nodatacow. Leaving /var as a directory under /, without specifying nodatacow concerns me as it is a very "busy" directory, and can fill up the root00 subvol quite quickly. I tried to create the two subvars, without success. I even went so far as to examine the grub menu entries. Is this not possible with Fed33 beta?