Add Flow Arrow between 2 Topics in OneNote Mind Map

Mind Map for OneNote add "Above Label" and "Below Label" feature. 
They provide flow arrow, you can edit them to marking the direction.

Select 2 Topics

To add "Above Label" or "Below Label", you need to select 2 topics at firs.
Follow steps:

1.     Click on a topic.
2.     Press "Ctrl" key, and click on another topic.

OneNote will select 2 topics.

Add Above Label and Edit Flow

After select 2 topics, click "MindMap" tab -> "Add Topics" group -> "Label" to add a little label above the connector between these 2 topics.

← Label →

Edit the label, remove ←, to making the direction to right.