Custom resolution for high resolution screenshots

As you may know, Unreal Engine 4 has this feature:

The problem is, is that it uses the resolution of the viewport and scales it up.

What I would like is that I am able to set a custom resolution for the high resolution screenshot, or at least for example 16:9 screenshot or 16:10 screenshot.

There’s a console command for that.

It would still be nice to add it there because it is easier to make screenshots with than type it in the console.