Need to add filter to register a template in [NEW] WordPress site editor through a plugin

[saadiqbal]

I am trying to add a new template in the WordPress site editor like this like this

but unable to do it with my custom plugin.

I have found a filter to register a custom template

add_filter( 'default_template_types', 'register_template_type' );

function register_template_type( $templates ) {
            $templates['help-us'] = array(
                'title'       => _x( 'Page: Help Us', 'Template Name' ),
                'description' => __( 'Displays Help Us template' ),
            );

            return $templates;
}

after adding this code I have figured out that by adding a file in the theme's template directory help-us.html I was able to register and display my custom template.

What if I want to add a custom template via plugin?

I was not able to find a way to add a custom template via the plugin. Previously I was using customizer in my plugin to customize the layout of a page with some custom functionality, now I am looking for a way to customize this page with the help of NEW site editor.

REF: ​https://wordpress.stackexchange.com/questions/417325/how-to-register-a-template-in-new-wordpress-site-editor-through-a-plugin

After going through, I figured out that we just need to make the template html file visible from the plugin to the template loop in order to display it. So I went over and added filter hooks in two places which just worked for me.

We need to add filters in following two lines;

1- wp-includes\block-template-utils.php:263

$themes         = array(
        get_stylesheet() => get_stylesheet_directory(),
        get_template()   => get_template_directory(),
    );
    // NEW Filter hook
    $themes = apply_filters( 'block_editor_templates_files', $themes, $template_type );
    $template_files = array();

2- wp-includes\block-template-utils.php:306

 $themes = array(
        get_stylesheet() => get_stylesheet_directory(),
        get_template()   => get_template_directory(),
    );
    // NEW Filter hook
    $themes = apply_filters( 'block_editor_templates_files', $themes );

Looking forward to your feedback and consideration.

Thanks