Default and Extended Window Controls
Accessibility settings are very important thing, it makes easier to use device for some people, without these settings it would be difficult or impossible. So, I came up with an idea, that will not difficult to implement, because GNOME already natively support Hide, Maximize (and of course Close) buttons on headerbar.
This is a window controls, with a choice of Default or Extended window controls. Extended option has Hide, Maximize and Close buttons. To make it harmonious with adaptivity and don't take up too much space, the Hide, Maximize and Close buttons would adaptive, turning into a short variant.