This is a handy “one-trick-pony” plugin. It’s only purpose in life is to display the ID of the page, post, or custom post type in the corresponding All Pages / All Posts listing.
Catch IDs is available in the WordPress Plugin Repository: https://wordpress.org/plugins/catch-ids/
There are many times when one needs the ID of the page, post, or custom post for other purposes. This plugin makes it ever so much handier than to hover over the page title, for example, and to look in the lower left corner of the browser to see what the ID is. Without needing your trifocals as I would.
All you have to do is install and activate it as you would any other WordPress plugin and it just goes ahead and does it’s thing.
A must have plugin in my book.