Tampere

See https://discourse.gohugo.io/t/feature-request-sitemapindex-for-sitemaps-with-50k-links/33214

Perhaps what you should be asking is how to split the sitemap list to multiple files. The 50k is a Google limitation, not Hugo's per se.

You need to see what you are customizing. Plus customization is a continuous process. So, having the server running when doing customization is the correct way.