Transforming Lights
Transformations can be applied by selecting a light in the treeview and moving its manipulators in the Viewer.
Note: See more about transformations in USD at Native USD Transformations.
Locally created Light prims will have MakeInteractive set to Yes by default, allowing interactive transformation upon creation.
In order to transform incoming prims, MakeInteractive would need to be set to Yes.
This will allow you to use the transformation handles found on the left side of the Viewer.
You can also right click on the light prim in UsdGaffer treeview and select Enable Interactive Transforms or Disable Interactive Transforms. This has the same effect as the makeInteractive parameter by turning the ability to make transformations in the Viewer on or off.
Note: You can find more information about the Engine system, and how to find the existing engines and their arguments in the Developer Guide > Usd Processing Engine > Engines.