Remove default jQuery

// Remove default WordPress jquery
wp_deregister_script( 'jquery' );

//Remove jquery migrate
add_action( 'wp_default_scripts', 'remove_jquery_migrate' );
function remove_jquery_migrate( $scripts ) {
	
	if ( ! is_admin() && isset( $scripts->registered['jquery'] ) ) {
			
		$script = $scripts->registered['jquery'];
		
		if ( $script->deps ) { 
			$script->deps = array_diff( $script->deps, array( 'jquery-migrate' ) );
		}
	}
}

Disable Auto-generated Image Sizes

// Disable Auto Generated Images Sizes
add_action('intermediate_image_sizes_advanced', 'disable_image_sizes');
function disable_image_sizes($sizes) {
	
	//unset($sizes['thumbnail']);    
	//unset($sizes['medium']);      
	//unset($sizes['large']);        
	unset($sizes['medium_large']);
	unset($sizes['1536x1536']);    
	unset($sizes['2048x2048']);
	
	return $sizes;
	
}
add_action('init', 'disable_other_image_sizes');
function disable_other_image_sizes() {

	remove_image_size('post-thumbnail'); 
	remove_image_size('another-size');
}

add_filter('big_image_size_threshold', '__return_false');

Add media file size column

Display the file size in a separate column in the Media screen

add_filter( 'manage_upload_columns', function ( $columns ) {
	$columns ['file_size'] = esc_html__( 'File size' );

	return $columns;
} );

add_action( 'manage_media_custom_column', function ( $column_name, $media_item ) {
	if ( 'file_size' !== $column_name || ! wp_attachment_is_image( $media_item ) ) {
		return;
	}
	$filesize = size_format( filesize( get_attached_file( $media_item ) ), 2 );
	echo esc_html( $filesize );

}, 10, 2 );

Add Featured Image column

add_filter( 'manage_posts_columns', function ( $columns ) {
	// You can change this to any other position by changing 'title' to the name of the column you want to put it after.
	$move_after     = 'title';
	$move_after_key = array_search( $move_after, array_keys( $columns ), true );

	$first_columns = array_slice( $columns, 0, $move_after_key + 1 );
	$last_columns  = array_slice( $columns, $move_after_key + 1 );

	return array_merge(
		$first_columns,
		array(
			'featured_image' => __( 'Featured Image' ),
		),
		$last_columns
	);
} );

add_action( 'manage_posts_custom_column', function ( $column ) {
	if ( 'featured_image' === $column ) {
		the_post_thumbnail( array( 300, 80 ) );
	}
} );

Set a minimum word count for posts

function snipjar_publish_min_words( $post_id, $post ) {
	// Edit the line below to set the desired minimum number of words.
	$word_count = 100;

	if ( str_word_count( $post->post_content ) < $word_count ) {
		wp_die(
			sprintf(
				// Translators: placeholder adds the minimum number of words.
				esc_html__( 'The post content is below the minimum word count. Your post needs to have at least %d words to be published.' ),
				absint( $word_count )
			)
		);
	}
}

add_action( 'publish_post', 'snipjar_publish_min_words', 9, 2 );

Disable new user email notifications

function snipjar_new_user_notifications( $user_id, $notify = 'user' ) {
	if ( empty( $notify ) || 'admin' === $notify ) {
		return;
	} elseif ( 'both' === $notify ) {
		// Send new users the email but not the admin.
		$notify = 'user';
	}
	wp_send_new_user_notifications( $user_id, $notify );
}

add_action(
	'init',
	function () {
		// Disable default email notifications.
		remove_action( 'register_new_user', 'wp_send_new_user_notifications' );
		remove_action( 'edit_user_created_user', 'wp_send_new_user_notifications' );

		// Replace with custom function that only sends to user.
		add_action( 'register_new_user', 'snipjar_new_user_notifications' );
		add_action( 'edit_user_created_user', 'snipjar_new_user_notifications', 10, 2 );
	}
);