Image Effects in editor? (5.4 from GDC)

In the Special Event video, the guy showing the "Adam" video shows/says that Unity 5.4 has a new feature that allows you to view image effects in the editor but completely neglected to explain anything like how anyone else can use it. The part where he starts about it is around 21:00.
I kept trying and I can't find anyway to do this in the 5.4 beta. He also is in Play mode the entire time but I don't know if that's a requirement (so I tried with and without it).

 

There was something in the release notes about it a couple of betas ago.

I think it's something that fx authors will have to update their assets for and not something that works automatically.

 

In the scene editor's environment toggle/dropdown button, there is a new entry called Image Effects. But it does not work. It's either not enabled in this beta or the image effects scripts have to be updated.

Update:

It works now!

You have to add [ImageEffectAllowedInSceneView] in the image effect scripts.

 

Wow, thanks. That's something clearly not well documented/announced.
They mentioned it here but unless you're a coder already familiar with scripting, that still wouldn't explain it.

I wonder if it's not going to be explained or mentioned again whenever the final 5.4 version is released, or if they'll make it easier to implement instead of manually pasting that into all the Image Effect script files (then removing), like a property checkbox.