login_form_middle is a WordPress PHP filter that allows you to add custom content in the middle of the login form, right after the ‘login-password’ field.
Usage
add_filter('login_form_middle', 'your_custom_function', 10, 2);
function your_custom_function($content, $args) {
    // your custom code here
    return $content;
}
Parameters
- $content(string): The content to display. Default is an empty string.
- $args(array): An array of login form arguments.
More information
See WordPress Developer Resources: login_form_middle
Examples
Add a “Remember Me” checkbox
Add a “Remember Me” checkbox to the login form.
add_filter('login_form_middle', 'add_remember_me_checkbox', 10, 2);
function add_remember_me_checkbox($content, $args) {
    $content .= '<p class="rememberme"><label><input name="rememberme" type="checkbox" value="forever"> Remember Me</label></p>';
    return $content;
}
Add a custom message
Display a custom message in the middle of the login form.
add_filter('login_form_middle', 'add_custom_message', 10, 2);
function add_custom_message($content, $args) {
    $content .= '<p class="message">Welcome! Please log in to access your account.</p>';
    return $content;
}
Display a privacy policy link
Add a link to the privacy policy page in the login form.
add_filter('login_form_middle', 'add_privacy_policy_link', 10, 2);
function add_privacy_policy_link($content, $args) {
    $content .= '<p class="privacy-policy"><a href="/privacy-policy">Privacy Policy</a></p>';
    return $content;
}
Add a “Lost your password?” link
Insert a “Lost your password?” link in the middle of the login form.
add_filter('login_form_middle', 'add_lost_password_link', 10, 2);
function add_lost_password_link($content, $args) {
    $content .= '<p class="lost-password"><a href="' . wp_lostpassword_url() . '">Lost your password?</a></p>';
    return $content;
}
Display a custom image
Add a custom image in the middle of the login form.
add_filter('login_form_middle', 'add_custom_image', 10, 2);
function add_custom_image($content, $args) {
    $content .= '<div class="custom-image"><img src="/path/to/your/image.png" alt="Custom Image"></div>';
    return $content;
}