It can be confusing for users that template parts are not always listed under "patterns"

[carolinan]

What problem does this address?

In Appearance > Editor , template parts are created and listed on the Patterns screen.
But in the Site Editor, template parts are not listed when you open the block inserter and select the Patterns tab.
This may be confusing and it makes footer and header template parts more difficult to insert.

Please see this support forum post: https://wordpress.org/support/topic/a-custom-footer-has-been-created-but-does-not-appear-in-the-list-of-compositions/

What is your proposed solution?

List template parts as a category on the Patterns tab in the block inserter, like on the pattern Data view screen.

[carolinan]

Also named template parts can not be inserted using /name