By adding labels to your flow, you can provide additional documentation in context. To add a label, click the "T" button on the bottom of the flow canvas.

Besides adding a label on the canvas, you can also add a label on top of a connector. To do that, select a connector and click the "T" button.

To edit a label content, you can double-click on it. You can simply drag a label around to move it. You can also manually adjust the width of a label by resizing it from the right edge.