By default KDE shows Firefox with border which looks not good. I use option "no border" in KDE menu. After this Firefox looks good, but there is no buttons minimize, maximize and close. I can't normal work with cutted window.
So, i use flag "browser.tabs.drawInTitlebar" and this returns buttons, but FIrefox now has white frame. This is annoying.

Any solutions to remove this white border and keep buttons?