What is View Layers Toolbox ?

It's a bunch of tools which helps you to manage your view layers, espacially with rendering

• Update passes : pick a layer as a reference, and your view layer will gain the same passes and aovs
  
• Update file outputs : this tool will create a compositing tree to render properly your render layers, regarding to your passes and your scenes outputs
  

Why is it useful ?

Because you will gain some time and will be able to deal with large amount of layers easilly !