function plt_hide_simple_slideout_menu_metaboxes() {
$screen = get_current_screen();
if ( !$screen ) {
return;
}
//Hide the "Slideout Menu" meta box.
remove_meta_box('simsa_slideout_me', $screen->id, 'side');
}
add_action('add_meta_boxes', 'plt_hide_simple_slideout_menu_metaboxes', 20);