multiQuerySource

Admittedly, I believe this is in regards to how the plugin has been configured by default depending on how many indexes someone is setting up to be a possible autocomplete suggestion source.

I’m looking into changes around some client implementation of the plugin myself, so I happen to have these links handy from some Algolia support discussion.

Please note that you could get your results from both indices in one query with our multipleQueries feature:
https://www.algolia.com/doc/api-reference/api-methods/multiple-queries/
To implement multiple queries on InstantSearch you can refer to the following documentation:
https://www.algolia.com/doc/guides/building-search-ui/ui-and-ux-patterns/multi-index-search/js/

Since you mention Autocomplete, I think this may be the page you want instead: https://www.algolia.com/doc/ui-libraries/autocomplete/guides/including-multiple-result-types/

As is, we don’t have any of this in the shipped version of the plugin, so it would be customizations needing made.

Welcome.