/interface ethernet switch port set 0 vlan-mode=fallback set 1 default-vlan-id=200 vlan-header=add-if-missing vlan-mode=secure set 2 default-vlan-id=200 vlan-header=add-if-missing vlan-mode=secure set 3 default-vlan-id=0 vlan-header=always-strip vlan-mode=secure set 4 default-vlan-id=300 vlan-header=always-strip vlan-mode=secure set 5 vlan-mode=secure /interface ethernet switch vlan add ports=switch1-cpu,ether4 switch=switch1 vlan-id=0 add ports=switch1-cpu,ether2,ether3,ether4 switch=switch1 vlan-id=200 add ports=ether2,ether3,ether5 switch=switch1 vlan-id=300 add ports=ether2,ether3,ether4 switch=switch1 vlan-id=400
0 - eth1-wan
1 - ether2-master (tagged 200,300,400)
2 - ether3-slave (tagged 200,300,400)
3- ether4-slave (Hybrid - native untagged (vlan0), tagged 200,400)
4- ether5-slave (Access port - untagged 300)
5- switch-cpu
This should work as Hybrid port (ether4) .. give it a try