If you are looking to know how to edit past revisions in Articles and Galleries,

You an find that here - https://intercom.help/formation/en/articles/10865127-editing-article-and-gallery-revisions.

The revision history feature is available for articles only and can be found on the top right-hand corner under Publish "History" section.

When you click on Publish History, a window opens and you notice the Compare revisions button on the top right side.

Click on it and you will be taken to a page where you can scroll through the different versions using a slider.

Use this slider to scroll through different versions of your article.

Note: You will be able to identify the revision version, the date of the revision, and any changes made to the hed, dek or body fields. The most recent version will always be on the right-hand side.

If additional text was added, the changes will be highlighted in green on the most recent revision version. If the text was removed, the text removed will be highlighted in red on the previous versions.

No changes: Every time you save, a new revision version will be created. If you save without making any changes, it will still create a new revision version and you won't see any text highlighted because no changes were made.

In this example, no changes were made in between saves, but new versions were created.

For articles on Ember/older Version, the Revision history button is at the bottom under Content History Section. When you click Compare Revisions, it will take you to the page where you can use a slider to view different revisions