CRS328 Series Switch Q in Q VLAN

Hi there

Just got in a CRS328-24P-4S, looked like a primo bit of kit, went about setting it up like i have my CRS2 series switches using Q in Q vlans.

Why is this not supported, the new /bridge/vlan set up is garbage compared to the CRS226 switch menu I use it as a service vlan switch and run multiple vlans inside those.

The switch chip(Marvell Prestera 98DX3336/3236) used in the CRS328 supports Q in Q so why not actually build ROS to properly interface that?
Otherwise I have a POE paper weight

Regards
Ben