Esc - for an exit from a player. One key Esc is much easier and faster to press, than to press a combination of keys Alt+F4 or Shift+X.
B - boss key. By pressing key B the player window is minimized and pauses playback.
A - next audio track.
Shift+A - previous audio track. By analogy to switching of tabs in windows in OS from Microsoft (Ctrl+Tab - next tab; Ctrl+Shift+Tab - previous tab).
S - next subtitle track. The key Z not so approaches. And here S it is the first letter of a word "Subtitle".
Shift+S - previous subtitle track. By analogy to switching of tabs in windows in OS from Microsoft (Ctrl+Tab - next tab; Ctrl+Shift+Tab - previous tab).
W - on/off subtitle.
Z - enter full-screen. I have a brother. He is right handed. To press the Enter uncomfortable. For him, it's best to press Z.
F9 - to switch off Audio Boost.
F11 - Audio Boost decrease.
F12 - Audio Boost increase.