Favorites Action for Elementor Pro Form allows you to add or remove favorite posts on the form submission.
You can set the Cookie or User Scope, where in order to allow the function to non logged users, you can use Cookie or employ the User scope to permit the current users to save favorite posts in their user meta.
Key: It is the unique name that identifies it in UserMeta or in Cookies. Pay attention when setting it, because if you change it you will lose the preferences saved until now (they actually remain saved with the old key, but they will not be considered).
It would be better to write it in lowercase, with _ instead of the spaces, and avoid special characters;
Post ID: Here you can dynamically set the current post "Post ID" or make use of the form fields to set the post ID(s).
You can also use Add to Favorites widget as an alternative, that is more useful, to allow adding posts to favorites via a button.
Showing the Favorites List
You can use the Favorites widget to show the list of favorite posts. Navigate to query and set the scope and key to fetch the favorite results.
You can also use Dynamic Tag - Favorites to display the list of current users' favorite Posts.