The way Makasu says is right if you only want to stop showing the hud, minimap, or hotkeys, if they already being displayed. If you want to disable the button completely use this,
$game_system.hud_button = true/false
$game_system.hotkey_button = true/false
$game_system.minimap_button = true/false
Just remember to turn them back on after
Also most of this stuff is in the manual under Utilities, which is section 3.2