Thank you very much for your kind words!
I'm not sure I udnerstand correctly, but I guess you want to create 6 separate search boxes to restrict the search to content from one speific parent-child category each. I believe this is what you are looking for: https://wp-dreams.com/knowledge-base/searching-within-given-categoriestaxonomy-terms-only/
Then I guess for the filters you can create the taxonomy term filters for each search box, by choosing which categories to display for each search instance on the Frontend search settings -> Categories & Taxonomy terms panel.Best,
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