To Reproduce: - Connect external mouse - enable option for touchpad "disable when external mouse is connected" - it works, touchpad is deactivated - then disconnect external mouse (maybe after some suspends) - the touchpad is NOT activated although mouse disconnected
KWin doesn't implement the option directly, it just exposes it from libinput. Please report this at https://gitlab.freedesktop.org/libinput/libinput/-/issues