I have two Add-ins that were installed via the Get Add-Ins button in Outlook. To be clear, these are not local Add-Ins, they are essentially loaded from the Office 365 service. I added them from my Microsoft Account, not a Work or School account. Both Add-Ins have been deprecated (Wunderlist and SAP Concur). As a result, there are placeholder icons that appear in Outlook (I believe their intent was solely for Outlook) toolbars, but they no longer function.
I cannot remove the Add-Ins. In the dialog for Get Add-Ins, neither appears in the section for My add-ins. I have seen suggestions on this forum to check the settings page in Outlook.com, but that does not appear to be available for the Microsoft Account version of Outlook.com, but that screen is identical in the web version.