ブロックエディタ　利用できるエディタを制限

function snippet_custom_editor_settings( $settings, $post ) {
 $settings['richEditingEnabled']= false;
 
 return $settings;
}
add_filter( 'block_editor_settings', 'snippet_custom_editor_settings', 10, 2 );

ブロックディレクトリ検索を停止

add_action(
	'plugins_loaded',
	function() {
		remove_action( 'enqueue_block_editor_assets', 'wp_enqueue_editor_block_directory_assets' );
		remove_action( 'enqueue_block_editor_assets', 'gutenberg_enqueue_block_editor_assets_block_directory' );
	}
);