The Shopify theme Dawn has a feature that allows you to add items to your cart directly from the product list (collection) page without going to the product detail page, but this is a way to make it work on search result pages as well. Since the appearance is almost the same, it can be implemented with only minor modifications.
How to enable the "Quick Add" feature on the search results page for the Dawn theme
Setup Step 1: Add a scheme to "main-search.liquid" and modify the display code
Step 2: Enable the "Quick Add" button in the theme editor search results template
