Adding multiple collections through blueprint?

How would I make this dynamic with blueprints? https://learn.getgrav.org/content/collections#multiple-collections

content:
    items: @self.children
    order:
        by: date
        dir: desc
    limit: 10
    pagination: true

fruit:
    items:
       '@taxonomy.tag': [fruit]

For example, I have a modular.yaml file and want to be able to add blog posts from an external collection and portfolio items from an external collection.

The example in the docs are

content:
    items:
      '@page.children': '/blog'

I'm not sure form your question which bits you are looking to make dynamic?