You must explicitly select the channel so that you can connect different devices. For example, set the mouse to channel 1 at the bottom of the mouse and connect your mouse to your USB dongle via the Logitech Unifying software (downloadable at https://www.logitech.ch). Once this happens, switch to channel 2. As soon as this happens, switch to channel 2 and you can establish a corresponding connection via Bluetooth without affecting your connection with the dongle. You can find more information in the user manual at logitech.ch.