In fact in the code base it is referred as “Document overview” and that’s how the button is labeled in the editor DOM.

The problem is there is not a single mention of this on this page, which is confusing. I spent 10 minutes to look for the documentation about this element to send to a client and I have 10 years of WP experience… I just could not remember how it’s called, looked at the code and searched for “document overview”.

I doubt I am the only one to have had this problem.
A name used in the editor page should maybe be used in the corresponding docs? Maybe? I dunno. A suggestion.

TYPO there:
“WordPress 6.3 renamced Reusable Block to (Synced) Patterns”