Hi JoelJBS,
Good day.
Thank you for connecting with us in Microsoft community.
According to your description, I and my other team members have checked few things from out side, but currently drag and drop functions does not support in Outlook desktop application under MacOS device.
Furthermore, I also believe that this is very important features under the Outlook application for MacOS device, I do understand your concerns about how it can help you be more productive in your busy daily work schedule, but since it's related Microsoft 365 product services and features under different devices, I believe that the related product team can develop some convenient configuration based on customer requests.
Therefore, Microsoft recommend submitting feedback by going in Exchange Online · Community (microsoft.com)
This community team and the Microsoft product development team are separate. Therefore, for features suggestions or design queries, users need to submit feedback to the Microsoft product design team from their side. Once a user sends feedback through the above means, it will sent directly to Microsoft and routed to the relevant product team so that can review it to do specific development in different OS devices.
To see more details on how to submit feedback, see this article Learn how to provide feedback to Microsoft - Microsoft 365 adminsMicrosoft Learning.
Since this is by design at this moment, I hope I have provided you with all the information you need about your requirements. If you need any further information from our side, please feel free to do so.
Thank you and have a nice day.
Sincerely,
Vaidya Darpan