My QC-35 headphones are most often simultaneously connected to my PC and iPhone. I play music from my phone and watch videos etc from my laptop.
The problem is: On many websites even if there is no sound the laptop "hijacks" the headphones. Nothing starts to play, but the music stops and audio moves to PC.
The only solution I have found is to manually from my bose app disable the PC connection. But that is time consuming and it is turned on again very soon. I also need the headphones connected to PC at times so I don't want to remove the connection totally.
You can adjust your PC's output settings so only music audio is played through. Notifications can be routed to output via the default output so it will prevent unnecessarily connecting when you get a notification.
To do this:
Open Settings > Sound >
Under Advanced sound options click:"App volume device preferences"
In this menu, change System sounds to your PC's default output.