This is a filter which is used to add custom fields to a registration form. This is NOT (yet) available through the admin.
See an example here.
- $extra_fields(array) - An array of extra field settings.
(string) An array of extra field settings.
- includes/actions-b3.php - line 340
- includes/actions-wp.php - line 35
- includes/filters-b3.php - line 61
- includes/class-b3-shortcodes.php - line 103
- includes/verify-filters.php - line 129