If you're looking for the source code for KWin, the window manager for the KDE Plasma desktop environment, you can find it on KDE's GitLab repository. Here's the link to the repository:
[KWin GitLab Repository](https://invent.kde.org/plasma/kwin)
You can browse the code, contribute, and even clone the repository using Git. If you have any specific questions about the code or need help with something, feel free to ask!