I like this for doing a conjunctive filter by Category and Tag. For example, to search for all articles tagged …
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Discovered this via Bill Erickson blog post of October 25, 2018. He uses it for Related Posts functionality. Pricing: $79, …
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ME: With this plugin you can customize WordPress search to search in Post Meta, Author names, Categories, Tags, or Custom Taxonomies via admin settings. You can control the default behavior of WordPress to search in the post title, post content, and post excerpt.