Do NE5000E/80E/40E support vlan stacking?
Yes, it supports vlan stacking.
[Quidway] interface gigabitethernet 1/0/0 enter into designated Ethernet view
[Quidway-GigabitEthernet1/0/0] portswitch set the port as switched port
[Quidway-GigabitEthernet1/0/0] port vlan-stacking outside-vlan 100 to 200 stack-vlan 9 Enable VLAN Stacking and 9 is public network Vlan.
Under default the port does not enable VLAN Stacking.