Is there an easier way to assign certain devices to set IP addresses?

I just migrated my system over and devices that had internally set IP addresses kept their settings, these were easy to assign with the app, merely choose "Advanced/Address Reservation" and select them. Renaming them is nearly as easy.

I wanted to give groups of devices (Echo units) addresses within a range (192.168.1.60 through 192.168.1.79). I was unable to set the reserved address outside of the DHCP assignment range. If I changed the DHCP range to include the address I wanted to use, I could modify it and then change the range back to normal.

I am not using subnets, I merely want to manage the addresses of devices in my network.

I hope I am just missing something obvious.