When changing volume, there will be a volume bar and volume percentage appeared.
Honestly speaking, the volume bar is reluctant and is blocking the view of the video. Is there a way in .conf to disable that bar?
You can do this with --no-osd-bar.
--no-osd-bar will disable the bar completely, for every command. You can also configure it on a per-keybinding/command basis in input.conf, e.g.
your_key no-osd add volume 2
And then there's also https://mpv.io/manual/master/#options-osd-on-seek