The presentations and exercises are not enough. You need to dig into the "docs" folder for several things (especially when you come to the firmware bit). But for what you're asking, the "simulation_user_manual.pdf" might help you. But again, it's been some time since I worked with the HDK.

We've done all that. I learned what the issue was, but it was due to lack of documentation, not us not looking enough.

The docs fail to mention that the Unity program is not the HMD Designer, it is merely a 3d viewer for the HMD Designer and the latter is actually written in Python and placed in a deeper subfolder called 'scripts'. To add to the confusion, the HMD Designer Viewer written in Unity cannot be launched by the user and must only be launched by the HMD Designer Python program, yet it fails to provide proper error or warning message when attempted to be launched by the user. The final confusing bit is that the HDK authors have not written an exe to launch the HMD Designer Python script with the correct pre-bundled Python, you can only start it from Steam, or you have to write your own exe launcher if you want the bundled python and python 3rd party libraries to be used, which is what we did, as not all my developers have the HDK on Steam.