Custom AOV are presented in the AOV Selector's Custom section, and can be selected for output to an image layer just like the built-in AOVs. A custom AOVs is represented by shading nodes of a specific type; the node's name defines the AOV name.
To create a custom AOV, simply pass connect a shader to a bind export node and give it a name. The AOV will then appear in the AOV Selector.
Note that the material has to be connected to a renderable object for the AOV to show up in the AOV Selector.
