Using the radio button mock up from @manueljlin I made an initial mock up of the window control buttons. I tried to keep a level of consistency without making it too taxing on lower resolution displays although having a hidpi one will greatly benefit the details.
https://www.figma.com/file/zZKHikCuBhbIf3NsP8BJ2S/Mk.4-KDE?node-id=146%3A50
I'm also doing Action Button based ones but I haven't gotten around to them a lot yet.