The following light filters are available in HtoA:
Light filters are created within Arnold Shader Networks and must be connected to a light output node. The vopnet is then connected to Arnold Lights under the Light Filter tab.
By default, when you click on the filters tab of a light, a vopnet will be created already within the light. Clicking the 'Jump To' arrow will take you inside obj > arnold_light1 > shopnet > arnold_vopnet. This is created here for convenience. However, an Arnold Shader Network vopnet could be created in the SHOP and linked to the light using the operator chooser.
When choosing the operator from the shop either the vopnet or the output node can be selected. If the vopnet is chosen and it contains multiple Output nodes then Arnold will use the first one it finds.
In your chosen vopnet Tab-type (Custom > Light Decay / Light Blocker / Gobo / Barndoor) to create a light filter node. Connect the output of the light filter node to the Light Filter # parameter of the light output node. As one is connected another empty input will be added. It is not possible to use more than one gobo or barndoor filter on the same light.