Note about dns-forward-max:
This option was never hidden. Users could always change it, but it was always considered a dnsmasq advanced option.
Pi-hole (including all previous versions) was able to use dns-forward-max option by adding a config file, as shown on this old post.
That's the new part (since Pi-hole v6).
Now, besides using the old method (using additional config files) you can also use misc.dnsmasq_lines to add a few configuration lines.