$plugins (array) An array of supported plugins (extensions).

$plugins = array(
   'page' => 'Extensions-Mainwp-Jetpack-Protect-Extension', // Targeted page.
   'slug' => 'jetpack-protect/jetpack-protect.php', // Slug of the plugin that needs to be installed.
   'name' => 'Jetpack Protect', // Plugin name.
),

add_filter( 'mainwp_plugins_install_checks', 'mycustom_mainwp_plugins_install_checks', 10, 1 );
function mycustom_mainwp_plugins_install_checks( $plugins ) {
   $plugins[] = array(
      'page' => 'Extensions-Seopress-For-Mainwp',
      'slug' => 'wp-seopress/seopress.php',
      'name' => 'SEOPress for MainWP',
  );
  return $plugins;
}