index.js

/**
 * Add categories attribute to core/latest-posts block.
 * 
 * @param {*} settings 
 * @param {*} name 
 */
function latestPostsCategories( settings, name ) {
	// Only modify latest posts block settings.
	if ( name !== 'core/latest-posts' ) {
		return settings;
	}

	settings.attributes.categories = {
		"categories": {
			"type": "array",
			"items": {
				"type": "object"
			}
		},
	};

	return settings;
}
 
wp.hooks.addFilter(
	'blocks.registerBlockType',
	'slug/latest-posts-categories',
	latestPostsCategories
);

/**
 * Add categories control to latest posts block.
 */
const categoriesOption = createHigherOrderComponent( ( BlockEdit ) => {
	return ( props ) => {

		// Only add option to latest posts block.
		if ( props.name !== 'core/latest-posts' ) {
			return <BlockEdit { ...props } />
		}

		const { setAttributes, attributes } = props;

		const {
			categories,
		} = attributes;
		
		return (
			<Fragment>
				<BlockEdit { ...props } />
				<InspectorControls>
					<PanelBody
						title={ __( 'Categories', 'slug' ) }
					>
						// Categories control goes here.
					</PanelBody>
				</InspectorControls>
			</Fragment>
		);
	};
}, "withInspectorControl" );
 
wp.hooks.addFilter(
	'editor.BlockEdit',
	'slug/categoriesOption',
	categoriesOption
);