In the post editor it is now possible to:

• Create a new custom block template on the fly
• If a block template is used, edit it visually in the template editor

In the case of user-generated block templates, the UI should provide a way for users to delete that template.

In the case of customised block theme templates it should be possible to revert those customisations and re-instate the theme default.

The Site Editor already offers a way to revert customised block theme templates:

This is something we can consider bringing to the template editor (albeit without the "Browse all templates" button for now). The same design can be utilised for deletion. Here's a rough mockup:

Since this would be a destructive action, we might want to expose a confirmation dialog that briefly explains the consequences of this action, something like:

Delete "My Custom Template"?
All posts that use this template will be affected.
[Cancel] [Delete]

It we could provide a count of how many posts would be affected, that would be even better :)

• Provide a way to revert customised theme-supplied block templates in the template edior
• Provide a way to delete custom block templates in the template editor