Flagged by Ricardo Couso
Article link: https://help.liferay.com/hc/articles/360032607571#example-searching-an-alternate-index
A) To make the sentence "to use the search bar's default query parameter (q)" effective, we should indicate that the field Custom Parameter Name should have the value "q" (without the quotes).
B) To get back actual values for the search data, it's important that the index mappings include `"store": true` for the different fields. By default this value is false, according to the documentation (https://www.elastic.co/guide/en/elasticsearch/reference/6.8/mapping-store.html#mapping-store). Some customers may not know this and find it difficult to find it.
C) The information about not having a query by default, namely "Since you're overriding the default query to search an alternate index, there's nothing in the query by default. Add any query clauses using the Custom Filter widget(s)." is quite important. It should probably deserved a more prominent place.