tml_ms_get_another_blog_signup_form()

function tml_ms_get_another_blog_signup_form( $blogname = '', $blog_title = '', $errors = '' ) {
    $current_user = wp_get_current_user();

    if ( ! is_wp_error( $errors ) ) {
        $errors = new WP_Error();
    }

    /** This filter is documented in wp-signup.php */
    $filtered_results = apply_filters( 'signup_another_blog_init', compact( 'blogname', 'blog_title', 'errors' ) );
    $blogname         = $filtered_results['blogname'];
    $blog_title       = $filtered_results['blog_title'];
    $errors           = $filtered_results['errors'];

    // phpcs:disable WordPress.WP.I18n.MissingArgDomain, WordPress.WP.I18n.MissingTranslatorsComment -- these messages intentionally reuse WP core's translated wp-signup.php strings verbatim, not TML-specific strings; no translators comments since they never enter TML's own .pot.
    $before = '<h2>' . sprintf(
        __( 'Get <em>another</em> %s site in seconds' ),
        get_network()->site_name
    ) . '</h2>';

    $before .= '<p>' . sprintf( __( 'Welcome back, %s. By filling out the form below, you can <strong>add another site to your account</strong>. There is no limit to the number of sites you can have, so create to your heart&#8217;s content, but write responsibly!' ), $current_user->display_name ) . '</p>';

    $blogs = get_blogs_of_user( $current_user->ID );
    if ( ! empty( $blogs ) ) {
        $before .= '<p>' . __( 'Sites you are already a member of:' ) . '</p><ul>';
        foreach ( $blogs as $blog ) {
            $home_url = get_home_url( $blog->userblog_id );
            $before  .= '<li><a href="' . esc_url( $home_url ) . '">' . $home_url . '</a></li>';
        }
        $before .= '</ul>';
    }

    $before .= '<p>' . __( 'If you are not going to use a great site domain, leave it for a new user. Now have at it!' ) . '</p>';
    // phpcs:enable WordPress.WP.I18n.MissingArgDomain, WordPress.WP.I18n.MissingTranslatorsComment

    $form = tml_get_form( 'another_blog_signup' );

    $fields = compact( 'blogname', 'blog_title' );
    foreach ( $fields as $field => $value ) {
        $field = $form->get_field( $field );
        if ( ! $field ) {
            continue;
        }

        $error = $errors->get_error_message( $field->get_name() );
        if ( $error ) {
            $field->set_error( $error );
        } elseif ( null !== $value ) {
                $field->set_value( $value );
        }
    }

    return $form->render( compact( 'before' ) );
}

View src/includes/ms-functions.php, line 1062 on GitHub