Redirect logged-in people away from the login page of PMPro.

pmpro-redirect-logged-in-people.php

<?php
/**
 * Redirect logged-in users away from the login page if already logged-in.
 * Add this code to your site by following this guide - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
 function my_pmpro_login_page_redirect() {
  global $pmpro_pages;
  
  if ( is_page( $pmpro_pages['login'] ) && is_user_logged_in() ) {
    wp_redirect( home_url( '/page-slug/' ) );
    exit;
  }
  
 }
 add_action( 'template_redirect', 'my_pmpro_login_page_redirect' );