Thanks, Ruud! I did it. And new PageType is added smoothly. In fact it was possible to add the new PageTypes, or at least I saw new PageTypes in the dropdown list. When I tried to delete some PageType WB returned error:
This page isn’t working
nocommentgroup.eu is currently unable to handle this request.
HTTP ERROR 500
Anytime, may be the future PageItems module will be more convenient for my needs. As I understand, it will add some fields to the usual WYSIWYG-pages and it will be possible to list pages with specific content of these fileds. May be it I should be patient for you to finish this module