The Full Site Editor brings the ability to create theme templates to WordPress core.
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This is a free plugin


Full Site Editor

Starting with WordPress 5.9 a new Full Site Editor was introduced. The Full Site Editor allows users to create theme templates using the drag and drop Gutenberg block editor. WordPress core introduced a very large number of placeholder blocks, available to all users, for standard site and post features that account for fields such as site logo, comments, as well as post title, content, featured image and so on.

Full Site Editing requires a theme that supports it. The new block-based themes all support the Full Site Editor. In theory regular "classic" themes could also, but so far none have.

Full Site Editor - The Good

The Full Site Editor is free and included with WordPress core.
The features of the Full Site Editor are being rapidly improved and extended.
Core now includes the Query Loop block. Although it can be clumsy to work with, it is the most powerful core block for creating custom post listings.

Full Site Editor - The Bad

There is no support for custom fields or conditional display.
Block layout and styling options are often limited and inconsistent.
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