CMB2
CMB2 is a developer's toolkit for building metaboxes
CMB2 is a developer-friendly library for creating custom meta boxes, fields, and forms in WordPress. It allows developers to add metadata to posts, users, terms, and more through an intuitive API. CMB2 is highly flexible and provides a variety of field types, making it ideal for creating complex custom fields within WordPress. It is actively maintained and can be extended through hooks and filters.