I just wanted to share an experience with the community.
I wanted to connect a Win10 laptop with Volumio running on Raspberry Pi 4 to play reference sound files of REW to characterize my drivers.
When connecting by bluetooth, Win10 is not recognizing the raspberry as loudspeaker (but as a portable media player), hence does not want to reorient the laptop audio to it.
I have edited the /etc/bluetooth/main.conf in the following way
class = 0x0c0414 (was 0x00041c before, 1c defines the object as being media player, 14 as a loudspeaker)
Enable = Source,Sink,Control,Media
MaxConnected = 1
Now when I am searching for bluetooth device from the laptop, rapsberry is appearing as loudspeaker and is able to play windows sounds after connexion.
Hope it could help some of you,