Last version osmand+ running, navigation volume can not be set seperately in the app (for example only 80% of system volume), when I'm on "media".
I haven't found it in the settings. Many other navigation apps do have this feature to seperately set the navigation speech volume instead of always the same volume level as the media output of the device.
This would be a great feature request, if it is not implemented yet (and I haven't found it yet).