My phone has Bluetooth.
Is there a way to connect Bluetooth headphones through my mobile phone to my PC i.e. use my mobile phone as Bluetooth dongle?
I can connect the phone to my PC using a USB cable.
In a separate step, you would use the usual device-specific way to redirect the Android audio output to your BT headphones.
The Android app is available in Free and Pro versions. The Free version interrupts your audio every 45 minutes or so.