TCAdefaults

This allows to set or override the default values of TCA fields that is available for various TCA types, for instance for type=input.

The full path of a setting include the table and the field name: TCAdefaults.[table name].[field]

This key is also available on Page TSconfig level, the order of default values when creating new records in the backend is this:

1. Value from $GLOBALS['TCA']
2. Value from User TSconfig (these settings)
3. Value from Page TSconfig
4. Value from "defVals" GET variables
5. Value from previous record based on 'useColumnsForDefaultValues'

However the order for default values used by \TYPO3\CMS\Core\DataHandling\DataHandler if a certain field is not granted access to for user will be:

1. Value from $GLOBALS['TCA']
2. Value from User TSconfig (these settings)

So these values will be authoritative if the user has no access to the field anyway.

Example:

# Show newly created pages by default
TCAdefaults.pages.hidden = 0

'ctrl' => [
  'useColumnsForDefaultValues' => 'doktype,fe_group,hidden',
  ...
]

If 'hidden' is in the list, it gets overridden with the "neighbor" record value (see \TYPO3\CMS\Backend\Form\FormDataProvider\DatabaseRowInitializeNew::setDefaultsFromNeighborRow) and as the value is set - usually to '0' - it will not be overridden again. To make it work as expected, that value must be overridden. This can be done for example in the Configuration/TCA/Overrides folder of an extension:

$GLOBALS['TCA']['pages']['ctrl']['useColumnsForDefaultValues'] = 'doktype,fe_group';