For the moment such search field is not included in the plugin. But you can always use WordPress default search field and to filter search results with Filter Everything. Here are examples – https://demo.filtereverything.pro/?s=nam&post_type=post and https://demo.filtereverything.pro/?s=apple&post_type=product
but, is it posible to filter the “Search Results” page?
I have tried what you indicate, but it’s a pity, because the solution of using the wordpress search engine takes you to the search results page, and it is no longer a filter, but a search 😉