In ~/.config/kwinrc, the property you’re looking for is under the group Windows named
BorderlessMaximizedWindows. You can edit this value to be false in your case.
Then you can do either of the following (depending on your WM) to activate the changes
kwin_x11 --replace
kwin_wayland --replace
The easier method, though, is to change it via the terminal directly using
kwriteconfig5 --file ~/.config/kwinrc --group Windows --key BorderlessMaximizedWindows false
qdbus org.kde.KWin /KWin reconfigure
This method will auto reload for you as well.
If you’re having trouble finding answers to something, sometimes it helps to search the question in reverse. By searching how to remove, I was able to find this answer.
In the future, someone like you might be searching the forum for this answer. With a title named “Dragonized KDE woes :S”, they are more unlikely to find the relevant information inside. Please consider making your titles related to the issue for the benefit of others.
Also, always post garuda-inxi or SGS is going to come get you! 
Had I had that information, I would have been able to give a more personalized answer based on your WM.