The settings screen is Settings → Reorder Posts. Administrators only. A link named Settings also shows on the Plugins screen. Nothing on this screen reorders a single post. It decides which types have a reorder screen, and whether front-end queries should be rewritten.
The form is one form. Switching tabs does not throw away the other tabs. Save still writes all of them. Add-ons can add their own tabs to this same screen.
Enable Post Types
Every post type with an admin UI is listed, except attachments. Posts and pages start enabled. Everything else starts off. A type with no admin menu still gets a Reorder shortcut on its row once you enable it. That shortcut is the way in.
Advanced
Only enabled types are listed. The heading on the screen says to leave this alone unless you mean to overwrite queries. I agree with that.
| Control | Values | Effect |
|---|---|---|
| Sort by | None (default) or Menu Order | None leaves queries alone. Menu Order rewrites front-end queries for that type |
| Sort order | ASC or DESC | ASC matches the drag screen. The control defaults to DESC if you have never saved it, so set ASC on purpose |
The rewrite applies on the front of the site: the blog home for posts, post type archives, WP_Query, and get_posts() when the query names one post type. It does not run in wp-admin, in feeds, or when the query names several types. While it is on, it replaces the sort those queries asked for. A Query Loop set to date will follow menu order anyway. Details and the narrower alternative are in Queries.
Reorder Posts
This tab is only the sample query shown at the bottom of a reorder screen. Yes shows it. No hides it. The default is Yes. The sample is a get_posts() call for the type you are reordering, sorted by menu order ascending. It is documentation on the screen, not a second save.
Where the settings live
They are one option, metronet-reorder-posts. Uninstalling the plugin deletes that option. It does not reset menu_order on your posts. Deactivating leaves both in place.