How to change register form action url?

FYI,
Previously(in v 6+) we were using something like this, in our custom register form template:

<form name="registerform" id="registerform<?php $template->the_instance(); ?>" action="<?php $template->the_action_url('register', 'login_post'); ?>" method="post">

at that time it was working fine, but don’t know how to modify this now, Please give me a direction for this.

Can you add the rft attribute as a hidden field to the form?

function add_rft_to_tml_register_form() {
    tml_add_form_field( 'register', 'rft', array(
        'type' => 'hidden',
        'value' => tml_get_request_value( 'rft' ),
    ) );
}
add_action( 'init', 'add_rft_to_tml_register_form' );