Highlight admin top level and submenu when viewing freemius pages.

fs-highlight-top-level-menu.php

<?php
/**
 * Highlight admin top level and submenu when viewing freemius pages
 */
function iconic_ecifw_menu_highlight() {

    global $plugin_page, $submenu_file;

    if( iconic_ecifw_is_settings_page() ) {
        $submenu_file = 'iconic-ecifw-settings';
        $plugin_page  = 'iconicwp';
    }

}

add_action( 'admin_head', 'iconic_ecifw_menu_highlight' );

/**
 * Check if we're on the plugin's settings page
 */
function iconic_ecifw_is_settings_page() {

    if( !isset( $_GET['page'] ) )
        return false;

    if( strpos( $_GET['page'], 'iconic-ecifw-' ) === false )
        return false;

    return true;

}