Gutenberg Detector
Which posts and pages use the Gutenberg Block Editor on your WordPress website? Find a list of posts created with the block editor through the Gutenberg Detector plugin.
Gutenberg Editor active status column
After you install this plugin, you will see a new column “Gutenberg Editor” in your posts and pages screen in the WordPress dashboard. “Yes” status next to specific posts implies – they have been created using the Gutenberg Block Editor.

A handy little plugin from Gutenberg Hub is very useful for older websites that use the classic editor for old posts and the newer Gutenberg Block Editor for new posts.