Creating a render2d in a new window?

I have a second window, and I’d like to have that lovely glow filter going on in it; is there an example floating around of how to do that, or just how to create a render2d in a new window? (It seems like that’s the only trick to it).

To my knowledge, render2d and aspect2d are just regular nodes locked to the camera and positioned/scaled to have certain properties. You should be able to create your own if you work out the geometry relative to your window size. You can also definitely create your own buffers and display regions to apply post-processing filters to. All of this is in the manual.