Use existing TCA fields

If you want to use already existing TCA fields, beyond the core fields, you can use an EventListener to modify the $allowedFields array.

EventListener example

EXT:some_extension/Classes/EventListener/MaskAllowedFieldsEventListener.php
<?php

declare(strict_types=1);

namespace VENDOR\SomeExtension\EventListener;

use MASK\Mask\Event\MaskAllowedFieldsEvent;

class MaskAllowedFieldsEventListener
{
    public function __invoke(MaskAllowedFieldsEvent $event): void
    {
        // Add field
        $event->addField('teaser');

        // Remove field
        $event->removeField('imagecols');

        // Get all allowed fields
        $allowedFields = $event->getAllowedFields();

        // Do your magic and set allowed fields
        $event->setAllowedFields($allowedFields);
    }
}
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Register EventListener

EXT:some_extension/Configuration/Services.yaml
services:
 VENDOR\Extension\EventListener\MaskAllowedFieldsEventListener:
   tags:
     - name: event.listener
       identifier: 'customizeAllowedFields'
       event: MASK\Mask\Event\MaskAllowedFieldsEvent
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Have a look at the official documentation for more information.