What do you mean? You mean a stripe, so similar to a traditional raid0? What would be what PVE calls Raid level "Single Disk" under "YourNode -> Disks -> ZFS -> Create: ZFS".
Alternatively you could do that using the CLI. See the "zpool create" command:
https://openzfs.github.io/openzfs-docs/man/8/zpool-create.8.html
So something like
zpool create -f -o ashift=12 UnreliablePool /dev/disk/by-id/YourFirstSSD /dev/disk/by-id/YourSecondSSD /dev/disk/by-id/YourThirdSSD
and then adding a new storage with
pvesm add zfspool UnreliableVMStorage --blocksize 16K --content rootdir,images --pool UnreliablePool --sparse 1 --mountpoint /UnreliablePool
Also keep in mind that you will need to keep your backups for longer than what you set up as scrub interval, as a raid0 won't offer any bit rot protection (just bit rot detection, but it can't fix data corruption).