XG Firewall - How to create static IP addresses

I'm hoping that this is a simple question, but for the life of me I cannot seem to find anywhere in the XG Firewall settings to set up static IP addresses based on MAC addresses.  This is very easy to find in UTM 9, but eludes me in XG.  My various home servers had static IP addresses to make them easy to find.

I would have thought it would be under "Interfaces" but no such luck there...

Thanks for any assistance.