Cathrine Wilhelmsen explains how to use Annotations and ObjectTags to store metadata in Biml:
There are two types of annotations in the Biml language. The first type is SSIS Annotations. An SSIS annotation is a comment inside your SSIS package that is visible on the design surface. This is what most SSIS developers think of when they hear the word “annotation”.
The second type, and the type covered in this blog post, is Biml Annotations. Biml annotations are more than just comments inside a package. They can be used to store additional string metadata on any Biml object, and can also be used in auto-generated documentation.
There are four types of Biml annotations: CodeComment, Documentation, Description, and Tag. You can read more about them in the official AnnotationType documentation.
I know I’ve underused Annotations in my Biml work, so this was good to read.