Covers the following filters:
page_attributes_dropdown_pages_argsquick_edit_dropdown_pages_args
The page_attributes_dropdown_pages_args and quick_edit_dropdown_pages_args filters fire when generating the list of pages available when selecting a post's parent. It's a documented way of modifying the pages available.
One existing used defined in WordPress/gutenberg#9089 is:
By using the filters, it is possible with Quick-Edit or Classic Editor to edit parent relations also for draft pages. This is important for some workflows because it may be necessary to create the whole structure before publishing. Unfortunately using the Gutenberg Preview functions deletes parent-relations for Draft-Pages.
Please open a new issue to suggest additional examples of existing usage.
There are no Gutenberg equivalents for this filter. See WordPress/gutenberg#9089 for discussion on how to accommodate.