Searching custom post types, selecting fields to search, post statuses etc..
Searching posts, pages and any other custom post types
To search custom post types, drag the post types from the left side of the container to the right side.
Custom post types option
Searching titles, contents, excerpts and other fields
On the same options panel, scroll down to select which fields to search within.
Searching in custom fields
You can either choose to search all custom fields, or search and select which custom fields to search within.
Searching all custom fields
For selecting custom fields, first turn off the Search all custom fields? option, then enter the custom field name to the search field - then drag it to the right side of the option.
If the custom field name does not appear in the list (like some Advanced Custom Fields ACF fields after creation), that means it is not yet have been assigned a value. When you create your first post with the newly created fields, and assign a value to it, it will appear in the list.
Known custom fields
_sku - WooCommerce product SKU field
Searching by categories, tags and other taxonomy terms
By turning on the Search in terms? option, the search within taxonomy terms (for posts and post types) is enabled.
Post statuses and password protected posts
By default password protected published posts are returned. You can add post statuses to the list (comma separated!), as well as turn off displaying password protected posts.