@marcus2812 That was what I tried back when I started the topic. It doesn't work for me at all...in fact it causes the KDE workspace to start flashing and flickering, and crashes KWin. It doesn't add the window border to Opera, and doesn't seem to survive a restart of Opera. There may be some other settings in that area....is it Application Settings or Window Settings?" What is the Window Class?
The only way I can get it to show borders is by manually doing the Alt-F3 sequence and manually turning on the borders. Then. I tried "Detect Window Properties" after manually turning on the borders....and that seems to have worked, including through an Opera restart.
Thanks,
Paul