TYPO3 Core

Most simple way to reproduce with a plain core:

Set:

    $GLOBALS['TCA']['sys_file_reference']['columns']['description']['config']['default'] = 'foo - hidden';
    $GLOBALS['TCA']['sys_file_reference']['columns']['description']['config']['renderType'] = 'hidden';

The create an image content element and add an image and save.

Expectation would be that description of the created sys_file_reference element has the value "foo - hidden"

Actual result is, that description is empty

Patch set 1 for branch 9.5 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/59898

Patch set 1 for branch TYPO3_8-7 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/59899

The patch works only for elements loaded the first time. If the record header is already there and the child content becomes fetched, the hidden field html is not included in the html output. Will create a pull request.

Hm, strange. Could have sweared that it also worked for ajax loaded elements. Can you post the change url of your proposed change here as well? Thanks!