Limit Modified Date
Warning This plugin is no longer supported, and does not always work with the Gutenberg block editor.
I recommend using Change Last Modified Date instead.
Summary
Prevent the modified date from changing when making minor changes to your content.
This plugin adds a checkbox to the Publish box, “Don’t update the modified date”. When checked, saving your post does not update the post modified date.
Minor changes like adding tags or fixing typos won’t bump the modified date.
This plugin will maintain the previous modified date. It does not let you specify a custom modified date.
When you’re ready to publish a major content change, you can uncheck this setting before saving the post.
Customization
Your theme will need to use get_the_modified_date() to display the modified date.
This plugin only applies to the post post type by default. You can customize which post types it appears on using the limit_modified_date_post_types filter.
add_filter( 'limit_modified_date_post_types', function( $post_types ) {
$post_types[] = 'page';
return $post_types;
});