Hi @ldittoe,
Welcome to Microsoft Q&A, and thank you for reaching out.
Based on your description, could you please verify whether this behavior is consistent? In my testing, when updating the attendee list for a meeting created/managed from a shared calendar, the ‘Send update to attendees’ prompt sometimes appears and sometimes doesn’t.
From my research, Microsoft documentation noting that the ‘Send Update to Attendees’ prompt behavior can vary depending on factors such as Outlook version and the Shared calendar improvements setting.
I suggest you try temporarily turning off ‘Turn on shared calendar improvements’ settings, restart Outlook, and then check whether the prompt appears more consistently when you only add or remove attendees. You can do this by go File > Account Settings > Account Settings, select your account > More Settings > Advanced and untick "Turn on shared calendar improvements"
I hope this helps.
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