What are recommended plugins for WooCommerce that show what customers are adding to their carts real-time before they check out?

Our eCommerce Analytics product (Metrilo) has one-click integration with WooCommerce and tracks what every visitor is doing in your eCommerce store. You can also filter people by their segment and see what products they were browsing and what products they've added or removed from their shopping cart. You can give it a try at this page https://www.metrilo.com/woocommerce-analytics. Private message me for an extended trial :-)

You are talking about something like Google Analytics Real Time Traffic.

I think it's much easier to bring back cart abandoners than understanding and solving the problems of cart abandonment. Usually cart/checkout abandoners are very hot leads, so all you need to do is bring them back to complete the purchase. Use GhostMonitor (https://ghostmonitor.com) to record all your abandoners and send them pre-built recovery campaigns to complete the purchase. It's completely free right now, you'll see all cart abandoners, and you can analyze your cart abandonment rate. I recommend do NOT start analyzing your checkout process and testing the fixes out, it takes an enormous amount of energy to do that, just send them emails, it will work. You can check other Wordpress plugins on https://wordpress.org/plugins/, but the GhostMonitor is the only one, who offers you pre-built campaigns, so you literally have nothing to do.