Quick Edit: do not apply level to non-hierarchical post types

[Offereins]

Context
In my code I have set my non-hierarchical post type unit to have a Page as a parent page (using the wp_insert_post_parent filter). That way I have ensured that all units will have the same parent in the site's hierarchy.

Issue
When viewing the units in the wp-admin/edit.php post list table, everything is fine. But when I'm updating a unit through the Quick Edit function, the updated row returns with a padded title, like — — Unit 13. While it correctly represents the hierarchy sitewide, the padding is irrelevant in the post list table, as all other units do not have such padded titles. Now those non-hierarchical posts are visually demoted. I would expect to have this behavior only apply to hierarchical post types. (Though the same issue might appear when the site's hierarchy spans beyond that very post type.)

Solution
The solution lies in wp_ajax_inline_save(), where the $level parameter is passed to the display method of the post list table class. I suggest the Two patches are attached to provide a solution. Patch 1 solves this issue just for non-hierarchical post types, and patch 2 extends 1) with only applying $level for the same post type.

[Offereins]

Do not apply level for non-hierarchical post types

[Offereins]

Do not apply level for non-hierarchical post types + limit to current post type

[chriscct7]

I'll clean this patch up on Friday night.

[ocean90]

@chriscct7 Any news on the refreshed patch?

[ocean90]

In 37913:

Posts: In wp_ajax_inline_save(), do not apply level for non-hierarchical post types.

Props Offereins.
Fixes #35010.