block-editor-settings.php

<?php

// See: https://developer.wordpress.org/reference/classes/wp_block_editor_context/.
add_filter( 'block_editor_settings_all', function( $settings, $context ) {
	// Curated blocks for the Widgets Editor.
	if ( isset( $context->name ) && 'core/edit-widgets' === $context->name ) {
		$settings['allowedBlockTypes'] = [ 'core/cover', 'core/heading', 'core/image', 'core/paragraph' ];
	}

	// Disable block locking controls in Site Editor.
	if ( isset( $context->name ) && 'core/edit-site' === $context->name ) {
		$settings['canLockBlocks'] = false;
	}

	if ( isset( $context->name ) && 'core/edit-post' === $context->name ) {
		/** Post editor setting overrides... */
	}

	return $settings;
}, 10, 2 );