I have several File (File Entity) and Content (nodes) types both referencing the same Topic taxonomy using the same field (one field, reused). The contents of these files/content are indexed in the same index using Search API (multi-type index). I also have a view that lists down the contents of that index, showing a mixed list of files and content.
Now what I'd like to do is filter the results by the Topic taxonomy using only one dropdown filter, e.g. If I want to find files and content related to "Science", I would just select "Science" from the Topic filter, and the view will show all the files and content related to "Science".
The problem is that when I add a filter to the view, Drupal presents two filter options for Topic, one for the Topic field on the File entity and another for the Topic field on the Content entity - not just one filter. I've already tried Combined Filters, but that doesn't give me a dropdown of Topics. Also hit a dead end on Search API aggregated fields.
How does one filter a view of both files and content by just one taxonomy filter?