Magento 2 uses catalog_category_change_products events to Checks if a category has changed products.
If you change an existing product from the category or adding new products to the category at that time, Magento use event for change products.
Declaration of the event from the vendor/magento/module-catalog/Model/ResourceModel/Category.php with a method, _saveCategoryProducts()
that add logic for the Save category products relation. Continue reading “Use of Event catalog_category_change_products Magento 2.”