You may remember these as reusable blocks from older versions of WordPress.
The current terminology is Patterns. They work very like the old reusable blocks.
While the creation of patterns is fairly intuitive. Renaming or deleting patterns is not at all obvious from within the WordPress dashboard. Therefore I was forced to consult the oracle in all such matters: ChatGPT.
Https:/wp-admin/edit.php?post_type=wp_block is the URL template you will need to access this functionality. For example this site would use: https://trialground.co.uk/wp-admin/edit.php?post_type=wp_block which may be a poor example because I haven’t created any patterns on this site.
For the moment this is here only as a reminder to self and I will complete it at a later date.