Reset parent_id of a PageTable field

[kixe]

Sometimes I had to reset/ delete parent_id in settings of a PageTable field to force items be placed as children of the page being edited.
I did this always by manipulating the database. Other way is to delete the field and create a new one. Both ways are not very comfortable. Is there a better way? Am I missing something? Would be nice to have this option from the field settings.