How to override the mmenu programmatically?

Enables or disables mmenu:

function hook_mmenu_alter(&$mmenus) {
  $mmenus['mmenu_left']['enabled'] = FALSE;
}

Enables or disables mmenu by conditions:

function hook_mmenu_alter(&$mmenus) {
  // Disables left mmenu on some specific pages.
  if (arg(0) == 'admin') {
    $mmenus['mmenu_left']['enabled'] = FALSE;
  }
}

function hook_mmenu_alter(&$mmenus) {
  // Disables left mmenu on some specific themes.
  global $theme;
  if ($theme == 'seven') {
    $mmenus['mmenu_left']['enabled'] = FALSE;
  }
}

Changes the assigned blocks:

function hook_mmenu_alter(&$mmenus) {
  // Resets the blocks to be empty.
  $mmenus['mmenu_left']['blocks'] = array();
  // Assigns new one.
  $mmenus['mmenu_left']['blocks'] = array(
    array(
      'title' => t('Management'),
      'module' => 'system',
      'delta' => 'management',
      'collapsed' => FALSE,
      'wrap' => FALSE,
      'menu_parameters' => array(
      'min_depth' => 2,
    ),
  );
}