Hi,
This documentation should be up to date: https://documentation.ajaxsearchpro.com/advanced-options/excluding-and-including-results/exclude-by-item-or-id
If you scroll down on that page, you should see an exclusion box by ID, as well as a search drag/drop field for easier exclusion.
Unfortunately there is no “exclude from search” functionality in core wordpress, that is only possible via 3rd party plugins or via custom code, or some themes may also offer an option for that. There are so many different solutions, that we would not be able to reliably support them.