When using the HDR Light Studio Blender Connection, we store the HDR Light Studio project data in the Blender scene file... but where?
You can find our data by looking at the Data API view. In the Scene > Scene section, towards the bottom of the list, you will find an entry called HDRLS Project Data.
You don't really need to mess with this. But if for some reason you did want to delete the embedded lighting project data, you can right click and select 'Reset To Default Value' to clear it.