How do I trigger a reindex with DocSearch?

It's not possible to manually trigger reindexing for DocSearch.

DocSearch crawls your site and reindexes once a day: https://docsearch.algolia.com/docs/faq#how-often-will-you-crawl-my-website

The DocSearch scraper follows the recommended atomic-reindexing strategy. It creates a brand new temporary index to populate the data scraped from your website. When successful, the crawl overwrites the old index defined in your configuration with the key index_name and deletes the temporary index.