View Quarantine add-in for Outlook Change Log
Please see How to install an Outlook add-in to view the Microsoft 365 End-User Quarantine for a full description and installation instructions.
UPDATE #1: Microsoft won't certify my add-in because they say it "does not provide significant value or benefits to commercial marketplace customers". I think most of you will disagree. I'll keep trying to get it certified, but in the meantime you can always install it from my website using the procedures from my blog article.