The new add-in will appear in the ribbon, grouped with the rest of the add-ins that you use today. With this new add-in rolling out, the existing functionality in Insider Fast, that this article talks about, will be replaced. Over this quarter, this add-in will roll out to customers in Production! This feature will allow you to send your mails and meetings to OneNote.
Outlook for Mac has been working closely with the OneNote for Mac team to move to the new OneNote add-in that is based on the Office add-ins framework.