How can I show a link to see all search results?
To show a link to see all search results, just go to the Other related products section of the Search box preferences and configure the All results link text field:
Note that you can use the tag {query} to show the current text typed by the customer. For instance, if configured as in the image above and the customer is searching with the text "a", the title will show:
Show all results for "a"
Note as well that if an empty value is configured, no link will be displayed.