This is the KWin port of the Portal effect of the Burn-My-Windows GNOME Shell extension. You can find a list of all Burn-My-Windows effects which are currently available for KWin on GitHub.

This effect requires at least KWin 6.0.0. Also, if the color picker widgets in the settings of any of the Burn-My-Windows effects do not work, you may have to install the package "libkf6widgetsaddons-dev" (Kubuntu, KDE Neon, etc) or "kf6-kwidgetaddons-devel" (Fedora, OpenSuse, etc). If you encounter a bug or have a feature request, please open an issue on GitHub!

IMHO, there are many things which could be done to improve the KWin port of the extension. However, since I am not using KDE as a daily driver, I would appreciate it very much if someone volunteers to work on this port! I am happily receiving pull requests...