> For example Firefox has the same design problem where its buttons have nor border and therefore have no clear place where draggable top space is and button is.
This can be changed by going to "about:settings" page and setting the option "browser.tabs.inTitlebar" to 0.
That about:config setting is a halfway okay solution for a single app, it loses vertical space however, which is my premium. Optimally I would like a way to (in all applications which has this problem) to _simply show me_ what is a UI widget/button and what part is "inert" draggable window chrome, like this older screen shot where the distinction is unambiguous and clear:
This can be changed by going to "about:settings" page and setting the option "browser.tabs.inTitlebar" to 0.