How to set opacity on a physical material?

I’m really confused, the description for opacity on a physical material in the docs (here) shows a slider for intensity.
However, when I create a physical material, it looks like this:

There’s no slider for actually setting the opacity. And when I try to put a black texture in there to see if that would make it transparent, nothing actually happens.

What’s going on? Has Playcanvas been changed and the docs not updated? If so, how do you make a transparent material now?

Or am I missing something really stupid/obvious here?!

Change the blend type on the material.

OK, nevermind. Just realised it depends on the blend mode!

Thanks yeah, just saw that!