In WooCommerce 3.6, the WooCommerce team announced Marketplace Suggestions (https://woocommerce.wordpress.com/2019/04/03/extension-suggestions-in-3-6/). These inject recommendations for official WooCommerce extensions into the Orders screen and the Products screen for the store owner. They were adjusted just prior to the release and will likely evolve in the next few versions.

There's a plugin on the WordPress site called Surbma | WooCommerce Without Marketplace Suggestions, which disables these promotions, as shown here:

At the moment, there's only one important line in the plugin:

add_filter( 'woocommerce_allow_marketplace_suggestions', '__return_false' );

The code to disable the promotions is quite simple: one filter that removes them completely.