After updated to Win 10 ver 2004, I again had a disconnection issue of the bluetooth mouse / keyboard due to the window automatically disconnecting to save battery power.
However, I cannot turn it off even though the older version of Windows 10 has a part like that here: https://support.microsoft.com/en-my/help/2758967/a-bluetooth- mouse-or-keyboard-fails-to-reconnect-after-being-left-idle
Anyone can help me to solve that !