Hi there,
At the moment there isn’t a way to add the name of the field group within the form because the form doesn’t “know” from which group the field is coming from.
An alternative way to add a title within that form, would be to modify the registration form template and add the title between line 27 and line 28 highlighted here https://github.com/WPUserManager/wp-user-manager/blob/master/templates/forms/form-registration.php#L28
You can use the $key variable to detect which field’s is being processed within the loop and accordingly decide where to put your custom html.
Example:
If the key of the field is wpum_my_own_field you can use that to display a title before the field’s output.
<?php foreach ( $data->fields as $key => $field ) : ?>
<?php if ( $key === 'wpum_my_own_field' ) : ?>
<h2>My title goes here</h2>
<?php endif; ?>
<fieldset class="fieldset-<?php echo esc_attr( $key ); ?>">
If you have any other questions about the custom field’s addon, please get in touch through the address support[at]wpusermanager.com because due to WP.org rules I’m not allowed to provide support for paid products through this forum.