PlasmaCore

KDE has actual documentation for PlasmaCore, which is the QML API used for creating UIs. PlasmaCore can also be used in declarativescript KWin scripts to create popups or dialogs.

Don't be too surprised if this documentation isn't remotely up-to-date either.

• org.kde.plasma.core

• org.kde.plasma.components

• org.kde.plasma.extras

• Plasmoid namespace (probably) not usable in KWin scripts.