Hi @ Nikki
Welcome to our forum!
Based on my research, there is currently no way to allow Outlook items to be dragged and dropped to other applications directly. I could drag and drop the emails or attachments from Outlook desktop client into browser, however, it is not opened directly, it is downloaded in browser and opened by default application. If you are serious about realizing this feature right now, I am afraid you need to use a third-party add-in.
Please kindly understand that many functions are not designed at present. At present, what I can do for you is to submit feedback for your request and I have post here, and you could vote for it. If you have any suggestions or ideas, it's suggested that you could post here. Hope Microsoft will notice this in the future.
Thanks for your understanding and support!
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