Multiple subnets/VLANs and hostname resolution

I've always wondered what the best way is to solve my problem of my multiple subnets and hostname resolution on the Pi-hole. Conditional forwarding works as intended but the interface only allows for one subnet with one domain name. I have 3 subnets that go through the Pi-hole so that entry doesn't suffice. What I've done is create a file /etc/dnsmasq.d/10-additional-dhcp.config and I have entered my subnet info in there so the file looks like this:

addn-hosts=/etc/pihole/local.list
addn-hosts=/etc/pihole/custom.list


server=/mgmt/192.168.1.1
server=/1.168.192.in-addr.arpa/192.168.1.1
server=/home/192.168.10.1
server=/10.168.192.in-addr.arpa/192.168.10.1
server=/iot/192.168.30.1
server=/30.168.192.in-addr.arpa/192.168.30.1

This allows hostname resolution for all those subnets. Meanwhile on the web interface it shows as no condition forwarding as being setup.

Am I doing this correctly? Is there a chance that there will be a change in web interface to allow more than one network to be entered? I wouldn't think that my situation is unique.

Why are these lines included? They duplicate existing lines in /etc/dnsmasq.d/o1-pihole.conf

Yeah I was wondering about those as well. I got the idea for creating that file from either here or reddit and I believe this was in the file from that example.

Is this file an accepted way to configure multiple subnets for conditional forwarding. It seems a little "hacky" so that's why I'm asking about it and if there will be a change somewhere down the line to do this through the web GUI.