Note: Native metafield editor should be used whenever possible first, however, in instances where this is not accessible this is an older solution that worked prior to Online Store 2.0 update
https://{SHOPIFY_URL}.myshopify.com/admin/bulk?resource_name={TYPE_TO_UPDATE}&edit=metafields.{NAMESPACE}.{KEY}
https://the-pages-media.myshopify.com/admin/bulk?resource_name=Collection&edit=metafields.global.promo_image%2Cmetafields.global.bg_image
Hidden from SEO Example
https://the-pages-media.myshopify.com/admin/bulk?resource_name=Pages&edit=metafields.seo.hidden
Reference: https://shopify.dev/api/examples/marketing-seo#hide-a-resource-from-search-engines-and-sitemaps
Shopify Dev Docs: https://shopify.dev/apps/metafields