How can I expand port forwarding?

If all positions are used at web NAT configuration (see below) you can use your own iptables rules in Startup Script.

Startup Script extensions of NAT configuration:

# forward rule
/sbin/iptables -t nat -A pre_nat -p tcp --dport 10016 -j DNAT --to-destination 192.168.1.26:80
# firewall permission
/sbin/iptables -t mangle -A pre_nat -p tcp --dport 10016 -j ACCEPT
 
# forward rule
/sbin/iptables -t nat -A pre_nat -p tcp --dport 10017 -j DNAT --to-destination 192.168.1.27:80
# firewall permission
/sbin/iptables -t mangle -A pre_nat -p tcp --dport 10017 -j ACCEPT