TYPO3 Core

Can reproduce it with 9.4.dev

master\typo3\sysext\backend\Classes\Form\FormDataProvider\DatabaseUserPermissionCheck.php function addData()
if (is_array($result['parentPageRow']))

$result['parentPageRow'] is null if editor creates a page at root. Admin user has a separate check and returns simple true

master\typo3\sysext\backend\Classes\Form\FormDataProvider\DatabaseParentPageRow.php
This class should return correctly null if root level is accessed.

Maybe its okay to use $result['neighborRow'] if $result['parentPageRow'] is null.

After that the saving throws this exception:
1: Attempt to insert a record on page '[root-level]' (0) from table 'pages' without permissions. Or non-existing page.

master\typo3\sysext\core\Classes\DataHandling\DataHandler.php
checkRecordInsertAccess() get a negative value via resolveSortingAndPidForNewRecord()

So a simple abs() does the trick

Patch set 2 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/57497

Is this the same issue? #81405

So you want to create a page as subpage of current page?

But if you use "New", the page is created (or tried to create) on same level as current page (under current page). I think this is currently not a bug, but it is not great either.

If you want to create a page as a subpage use the context menu: "More options" > "Create new wizard".

I think this is actually a duplicate of #81405 and should be closed.