TYPO3 - IRRE Element in normal Content Element

Question

is it possible to put an IRRE-element into an new content element without an extension? I tried to get it work but it wont.

'keyfactitem' => [
    'exclude' => true,
    'label' => '',
    'config' => [
        'type' => 'inline',
        'foreign_table' => 'tt_content',
        'foreign_field' => 'keyfact_container',
        'maxitems' => 3,

        'overrideChildTca' => [

        ],
        'behaviour' => [
            'localizeChildrenAtParentLocalization' => true,
        ],
    ],
],

This is what I got in my TCA Override for a new Content Element. I got the select for a new Child Element (see in the Picture below) Image IRRE Child

So my problem is that i got a new Content Element in the backend and in the IRRE element. Take a look at the following picture.

Backend

Somebody who can help me out here?

(Btw. TYPO3 9.5.4)

Answer 1

As it is done with Gridelements, Flux or Mask you will need a new colPos value for children, that will be invisible but not marked as unused in the backend.

So you will need at least that value and a method to deal with the unused settings. Take a look at Gridelements to see how it is done.