Selection of parent category when creating or editing category

[pbe]

Hi,
when creating or editing a category in Phoca Cart 6.0 (Joomla 6.0.4) and trying to select the parent category, not all categories are listed/available in the drop down list.

[pbe]

Just explored the topic a more. Seems just all categories that already have a parent category set are not listed in the drop down list.