Just to share if somebody need to extend custom field types (textarea example)
Add this code near line 160 in application/helpers/custom_values_helper.php
<?php break; case 'TEXTAREA': ?>
<textarea id="<?php echo $custom_field->custom_field_id; ?>" name="custom[<?php echo $custom_field->custom_field_id; ?>]" class="form-control" value="<?php echo $fieldValue; ?>">
<?php echo $fieldValue; ?>
</textarea>
And replace/add ‘TEXTAREA’, to code near line 34
‘TEXT’,
‘TEXTAREA’,
‘DATE’,
‘BOOLEAN’
You can add whatever field type and make customization per your needs…