Here's the workaround for wanting to add the Image Description directly to the Media Library rather than just the post, which leaves the description in the media gallery blank. There's three simple steps. Follow along pictures and video.
Posts for designers, developers, and bloggers about the world’s most popular CMS, WordPress.
As a web developer, I’ve worked in WordPress in many capacities. I’ve developed themes from scratch, inherited themes, bought themes, built and managed shops on WooCommerce, and worked in Gutenberg and third-party builders, including Avada Builder, Beaver Builder, and WPBakery. This space is a collection of learnings during this process.

