When you index a metafield in the Algolia Shopify app with the "Use as facet - Yes" setting enabled, the metafield attribute will automatically appear in the Inactive facet list within both the InstantSearch and Collections Facets configurations.
However, if your metafield is in JSON format with nested attributes, even if you've enabled the "Use as facet - Yes" setting during Metafield indexing, please note that nested attributes will not appear in the Inactive Facet list, as these need to be indexed separately.
While you can manually add Custom Faceting Attributes in the InstantSearch > Facets configuration, please note that custom facets added in the InstantSearch Facets configuration will not automatically sync to the Collections Facets configuration. Currently, the Collections Facets configuration does not support adding custom facets.
InstantSearch Facets Configuration - Adding custom facets ✅
Collections Pages > Facets configuration does not support Adding custom facets ❌
We are aware of this limitation and are working on adding this feature to the roadmap for Algolia Shopify app. In the meantime, if you'd like the manually added custom facets in the InstantSearch Facets configuration to be reflected in the Collections Facets configuration, please reach out to the Algolia Support team (https://support.algolia.com/hc/en-us/articles/4406981896593-How-to-contact-support).
We'd be happy to assist in copying the InstantSearch Facets configuration over to the Collections Facet configuration to keep both aligned.