Planner is a great light-weight project tracker that’s part of Office 365, and Microsoft continues to roll out changes that make it even more useful. One of the latest features (and one could argue it should have already been there) is the ability to set a Priority on a task. Here’s how that works…
In the metadata area for a specific task, you’ll now see the Priority dropdown field:

You have five categories to choose from:

You also have the ability to group all your Planner tasks by Priority:

This is a much-needed feature in Planner, and helps me to focus on the things that are most important instead of being swamped with tasks that are seemingly random in their importance.