When creating pages to add inside a page, the plugin doesn't respect the post status and works without regard to if the parent page is a draft.
I believe this isn't intended behavior, as according to a note in the changelog for CMS Page Tree View (also made by the same developer),
no longer allowed to add sub pages to a page with status draft, because if you edit the page and save it, wordpress will forget about the parent (and you will get confused)
Sorry, can't create a sub page to a page with status "draft".
Admin Page Tree View should probably share the same behavior.