There are a few questions about "showing buttons" but these are not what I want. Here's the System Settings's window buttons as it has always been.
And here's what I want in all windows. For example, in the System Settings menu, you can't maximize the window. But I want the maximize button in the window EVEN if we can't do anything with it. Likewise when we can only CLOSE the window, I want the maximize and minimize buttons anyway. The design of the unclickable buttons is from the one of an inactive window.
Even if it's unclickable I want it in the windows
Q: So, can we make anything like that by editing some files or dconf or something else? Just always show close, minimize, maxmize buttons.
I am ready to break my Ubuntu, it's just a testing Ubuntu.
EDIT: Still don't know how to do, but I found a window that show what I want, in "vanilla" Ubuntu.
So here's the normal window: 
And when I maximize the same window I get what I want in the normal window: 
Q: So is there a way to get the line(s) of the config file(s) that makes it possible to get this?
Best Answer
Short answer is no, you can't do this in a trivial manner by just changing settings.
Long answer is that you need to edit the theme to draw the button anyway (probably you want to draw the unfocused version on focused windows), for the specified title bar hints in the theme.