When in the Stream of Google Classroom you can find the topics listed on the left-hand side. Click on the topics in the listing to filter assignments for that topic.
You can add a topic by clicking on “Add topic” in the sidebar.
Alternatively, you can add a topic when creating an assignment. By default an assignment has “No topic.” Click on the tiny triangle next to “No topic” and click on “Create topic” at the top.
Think outside the box of the traditional topics you would have used in your gradebook. Instead, think… how will students FILTER the Stream. Create topics around what would make filtering useful, not simply by category. You’ll likely change your mind and need to edit your topics. In the sidebar on the left, hover over a topic to reveal the 3 dots options. Click on the 3 dots to either “Rename” or “Delete” a topic.