Redirecting after login except for a specific page

You can achieve this by modifying your custom_login_redirect function to include a conditional check based on a parameter you pass from your specific page. Here’s an example of how you can modify your function:

function custom_login_redirect($redirect_to, $request, $user) {
    // Check if there is a user and if the user has roles
    if (isset($user->roles) && is_array($user->roles)) {
      // Check if the login request comes from your specific page
      if (isset($_GET['from']) && $_GET['from'] == 'special-page') {
        // Do not redirect
        return $redirect_to;
       } else {
        // Redirect to '/main_report' or another specified page
        return home_url('/main_report');
      }
    } else {
      // Default redirect if there's no user 
      return $redirect_to;
    }
}
add_filter('login_redirect', 'custom_login_redirect', 10, 3);

If modifying the login form is not possible, or if you prefer not to use GET parameters for tracking the origin of a login request, you can use PHP session variables as an alternative. This method involves setting a session variable when a user visits your specific page and then checking this variable during the login process.

function set_login_origin_session() {
if (is_page('your-specific-page-slug')) {
    // Start the session if it hasn't already been started
    if (!session_id()) {
        session_start();
    }
    // Set a session variable to indicate the user came from the specific page
    $_SESSION['login_origin'] = 'specific-page';
   }
}
add_action('template_redirect', 'set_login_origin_session');

function custom_login_redirect($redirect_to, $request, $user) {
  // Check if the session variable is set and equals 'specific-page'
  if (isset($_SESSION['login_origin']) && $_SESSION['login_origin'] === 'specific-page') {
    // Clear the session variable to prevent unintended redirects in future logins
    unset($_SESSION['login_origin']);
    
    // Do not redirect; return the original destination
    return $redirect_to;
  } else {
    // Redirect to your default location
    return home_url('/main_report');
  }
}
add_filter('login_redirect', 'custom_login_redirect', 10, 3);