I have set up LG webos add-on and homekit add-on. I was able to add Switchable metadata to TV Power model and it’s working fine. Next thing i want to add is Speaker,Speaker.Volume metadata to TV Volume to control the volume but it shows on the mobile phone that it’s not supported. When I use light dimmer for controlling the volume it is working but I want to use the speaker and not Lighting,Lighting.Brigthness, because when clicking the light widget it will set volume to 100% 
I used this metadata for making the volume work as lighting dimmer:
value: Lighting,Lighting.Brightness
config:
homekitdimmerMode: filterOn
I tried to change Lighting to Speaker and Volume, but did not work. any suggestions?