Thank you for contacting us, in Activity, the commands that are automatically generated at creation can't be deleted, you can change them in the device (Device--Edit--power setting) and they will be automatically updated in Activity after the changes are made.
Regarding your mention that the device will be turned off when switching Activity, CEC may also lead to device switching state conflict, it is recommended to turn off the CEC function of the device. Avoid sending commands to the device via HDMI as well when other devices are turned on/off, this may duplicate with activity commands and lead to control exceptions.
Also you mentioned the Back button at the top of the screen, this button is used to control the screen, the Back button to control the device is in the middle of the remote control. Regarding your suggestion, we will also share it with our R&D team. We appreciate it.