With Samsung Smart TVs that support the multiple audio output function, you can output the sound simultaneously via the TV speakers and Bluetooth headphones. The volume of the headphones and speakers can be set independently of each other. If the speakers are switched off, the sound is automatically output via the headphones and you can adjust the volume of the headphones yourself.

I cannot confirm whether the specific model QE43QN90D supports this function, as the exact functions depend on the model. It is advisable to consult the TV's instruction manual or visit the Samsung website for specific information.