make custom metadata (fields) definitions as easy as defining smart collection criteria

As early as 2011, people started to ask for custom metadata field support.  See this long-running thread.

https://community.adobe.com/t5/lightroom-classic-ideas/p-allow-users-to-define-custom-metadata/idi-p/12249885

Adobe invented XMP back in ... 2001, six years before releasing Lightroom V1, but has never provided custom metadata support in Lrc.  For the average Lightroom Classic user, creating a customer metadata definition needs to be as simple as defining smart collection criteria.  And it needs to easily shared with other users.  And the SDK needs support for plug-ins for import, search, export, etc.

At present, custom metadata fields for DAM products are confined to enterprise-level products, with a price tag to match.