Collections are a great new tool to better organize your content! Collections essentially act as folders within your categories.
To create a collection, select "Library" on the lefthand Portal column, then "Collection" at the top tab bar.
When creating a collection, you'll add a category (or subcategories), and then add classes from your existing library.
You'll add your collection to a category, just as you'd add other classes/content! This is how a collection will appear in-app:
