"Block New Devices From Network"
I noticed the "Network Lock" request here: https://community.eero.com/t/k9bygw/network-lock
I was actually thinking something similar but implemented differently. Rather than a "Network Lock" toggle it might be nice if there were something like a "Block New Devices From Network" toggle.
Any new device that joins the network would simply be blocked, and a notification could be sent that a new device has joined the network and been blocked.
The advantages to this implementation are that you'd get a notification on join and you wouldn't have to toggle the setting to get new devices on the network (you could just unblock the new device to let it on the network).