ninja-forms-example-settings-plugin-settings-groups.php

<?php

function plugin_settings_groups( $groups )
{
    $groups[ 'example' ] = array(
        'id' => 'example',
        'label' => __( 'Example Settings', 'ninja-forms-example' ),
    );
    return $groups;
}
add_filter( 'ninja_forms_plugin_settings_groups', 'plugin_settings_groups', 10, 1 );