With kwin/KDE5 it's no longer possible to customise the spacing between the buttons in the window title. This used to be an excellent usability aid in KDE4 as it allowed one to clearly separate the window close button from the maximise/minimise buttons and thus greatly reducing the chances of a mis-click. Reproducible: Always
*** This bug has been marked as a duplicate of bug 348393 ***
Created attachment 96752 [details] An example of a KDE4 setup with clearly separated buttons