I'm in the process of migrating my entire network setup to an Unifi network. For this purpose I've bought an Unifi USG, S8-60W and two access points.
My incoming internet (and IPTV) is Kpn FTTH, and I will blog about the basic setup of that in a few days. But once it was running the first thing I wanted to do was create a static host in the dns of the USG.

Why? Well, I've also got a synology NAS running on the local network which I expose to the external network (by forwarding the port). And I've added a hostname on my internet domain, to be able to request a Lets Encrypt certificate for that.
So I want same hostname on my local network to resolve to the local nas address, so the certificate is also valid. This can be done with an entry in the hosts file on my machine ofcourse. But an entry in the dns server of the USG is much nicer.

Ssh into the USG, and open the vi editor to create a new file:
sudo vi /etc/dnsmasq.d/dnsmasq.static.conf

And there add the host and ipaddress:

And save that. Now activate that with:
sudo /etc/init.d/dnsmasq force-reload

This trick will survive reboots and reprovisioning. But was overwritten by the last firmware update I did.