How to bind BACKSPACE?

[LinArcX]

I want to use backspace to go back to up_dir. This is what I've done:

  {
    "key": "BACKSPACE",
    "command": [ "script-binding", "file_browser/dynamic/up_dir" ]
  },

But it's not working. Any idea?

[CogentRedTester]

The key code mpv uses for backspace is BS, not BACKSPACE.