The PrmanOutputChannel define node in katana is pretty straight forward, using the source param you add for ie a beauty lpe as:
color lpe:C[DS]*[<L.>O]
What if you want to add your custom lpe to the predefined list? Renderman comes a list of built-in predefined lpe (docs) such as lpe:specular, lpe:diffuse, lpe:shadowcollector, etc
You can add your own by adding a lpe macro to your rendermn.ini
/prman/lpe/macro/beauty C.*[<L.>O]
Now you can use this new “beauty” by setting your PrmanOutputChannelDefine.name as lpe:beauty If you want to render a lightgroup called “key”, set it to lpe:beauty_key
And you can always add your project predefined lpes per ligthgroup as well