How to customize Post Edit or Post Add New of admin screen.
Manage meta boxes
You can be able to hidden/remove/rename the title of meta boxes.
If active the Gutenberg(Block Editor)
Block editor meta boxes customize is possible to hide the meta boxes of right sidebar, meta boxes recognition is not necessary reload because all meta boxes is static items at now.
If active the Classic Editor
Classic editor meta boxes customize is possible to hide or remove or change the meta box title, meta boxes recognition is necessary reload post edit screen because all meta boxes is dynamically items.
Note: If you get problem with meta boxes customize, it most cause of problem is delete the meta box. Some themes is not have consider delete the meta box, so please change the hide from remove meta box.
Change the post edit messages.
Change the Editor
Change the post edit Editor(for WP ver 5).
Hide Add New
Hide Add New is next to page title name of post edit.
You can not input/change the post title.
Change title placeholder
You can change the title placeholder from Enter title here.
Change Post title to Post ID
Restrict the post title to Post ID. If you use, recommend hide with Hide Title.
Hide Permalink to current post link.
Hide Change Permalinks
Hide Edit button of change permalink.
Hide Content editor. If you use, recommend use with some custom fields meta boxes.
Re-arrange meta boxes
Post edit users is not be able to Drag&Drop to meta boxes.
Forced Editor (for Classic Editor)
Post Content editor is restrict the editor.
Publish metabox (for Classic Editor)
Some items is can be hide.