This is a multi-purpose toolbar, that allows dragging and dropping onto the various icons. You will use these icons extensively while building your Flow Model.
For example, if you want to quickly create a new Model folder, you can drag the Folder icon at the top of the Flow Zone directly into your Model view. Similarly, use the other icons to create Events, Metrics and Measures.
The Flow Zone can also be used to drop Model items. For example, if you drag a Measure from your Model view onto the Calculator icon, Flow Config will create a new calculated Measure for you.