Again, why?
I’m not trying to sound rude, but what is the practical reasoning for installing Manjaro to a ZFS root?
It’s overly complex to do in the first place, and there’s greater risk in maintaining and updating your system.
ZFS on your NAS makes sense.
On a dedicate data storage pool (on a Manjaro system) makes sense.
Heck, one could argue that it’s not too far-fetched (but still with some inherent maintenance risks) to use for your /home.
But why the root system?
If you’re dead-set to use Manjaro on a ZFS root, then I wish you the best of luck. I just want to chime in that I personally am a huge fan of ZFS (I use it a lot!), yet I will not install Manjaro to a ZFS root.
Reconsider using BTRFS (if you want snapshot rollbacks with Timeshift), or the tried-and-true EXT4 or XFS.