In Windows Desktop Outlook this button is in the Add-ins button group as indicated by the text 'Add-ins' as the label below the button. Look at the Microsoft Store red briefcase 'Store' button for example. Outlook for Mac does not appear to have button group labels. That mostly seems to be the case but we noticed an issue with Outlook for Mac. Outlook add-in manifests are supposed to work on PC Desktop Outlook, OWA and Outlook for Mac.
