The problem: When "Hide default translation of page" was set for a page, the page disappeared in the menu for ALL languages. Therefore it was not possible to create pages only in Dutch (whith English being the standard language).
In ``TYPO3\CMS\Frontend\ContentObject\Menu\AbstractMenuContentObject::filterMenuPages(&$data, $banUidArray, $spacer)`` (in the file typo3/sysext/frontend/Classes/ContentObject/Menu/AbstractMenuContentObject.php) replace::
// Checks if the default language version can be shown:
// Block page is set, if l18n_cfg allows plus: 1) Either default language or 2) another language but NO overlay record set for page!