With phones losing headphone jacks, people are relying more and more on Bluetooth headsets and accessories. And it seems Google wants to make life easier for users who are reliant on the technology. An AOSP commit titled “Implement Bluetooth device volume memory” shows the possibility that the next Android version, which we call Android P, will be able to remember the volume of your Bluetooth devices. Bluetooth volume memory, as the commit describes, will be handled on a “per-device basis.” The volume profiles will be stored in shared preference and will be loaded every time the device is connected. The description adds, “Volume is persisted for devices that both do and don’t support absolute volume.”
There is currently only one master volume for Bluetooth devices but with the possible introduction of volume memory being handled individually, it takes out the hassle of having to adjust volume each time you connect your phone to your Bluetooth accessories.
Source: Android Authority