You can operate on tables and table members from the command line.
$ sudo pfctl -t clients -T add 192.168.10.16 $ sudo pfctl -t clients -T show $ sudo pfctl -t clients -T replace -f /etc/clients $ sudo pfctl -t clients -T delete 192.168.10.16
and yes, you can have
table <clients> file "/etc/clients"
in your pf.conf