@luxflow made this a default. So, this should not be a problem.
Are you sure? I started ZFS installation on OMV in February 2017 with ZFS plugin version 3.0.9 and I had to edit also the file /etc/default/zfs and to add
ZPOOL_IMPORT_PATH="/dev/disk/by-id",
because it was missing.
There was already this entry
#ZPOOL_IMPORT_PATH="/dev/disk/by-vdev:/dev/disk/by-id"
but it was commented.