I can access Message (mail) and Appointment objects via the office-js library and show the add-in button within these objects to show the pane.
Is there any way how to show the pane in the Task object window?
Thank you for any hint. I suppose it is not just supported now and I will have to manage Tasks via Graph API. https://learn.microsoft.com/en-us/graph/overview
Currently, add-ins are not supported on Task items, only appointments and mail messages. We track Outlook add-in feature requests on our user-voice page. Please add your request there. Feature requests on user-voice are considered, when we go through our planning process.