Hi @Ruby Sharma ,
Welcome to our forum!
As I know, it's not available to create a keyboard shortcuts for add-ins in Outlook. I'm afraid you still need to close it with a mouse click. For more information, please refer to: Add custom keyboard shortcuts to your Office Add-ins.
If you really need this feature, it is recommended that you could post the functions you expect on the website dedicated to collecting feedback. We sincerely welcome your suggestions, and thanks for your understanding and support!
In addition, considering that the screenshot you provided contains personal information, I have hidden it in order to avoid privacy disclosure. Please remember to hide your personal information before uploading.
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