You can find the search filter under Settings in the WP Search Insights Dashboard under Tools.
You might have issues with recurring spam queries, or people trying to search for URL’s and other search queries that might make your data analysis troublesome. You can manually block these queries with the search filter.
The search filter only matches when the added query is equal to the used query. For example:
should be added both, as they are not the same. This is true for spelling mistakes as well.
TIP: if you are frequently deleting queries from your dashboard, make a habit of adding non-relevant spammy queries to the search filter as well.