Keep the last modified date unchanged for minor post updates.

Ultimate Last Modified Plugin for WordPress with Gutenberg Block Integration. It is possible to use shortcodes to display last modified info anywhere on a WordPress site running 4.7 and beyond.

Adds the last modified time to the admin interface as well as a [last-modified] shortcode to use on the front-end.

Show modified date column in the lists of pages and posts in the WordPress admin panel.

Add modified date sortable column, featured image custom column to the admin interface for post and pages.