Upgrade direct install software from App Store I have Microsoft Office installed on my Macbook Pro which I downloaded from Microsoft's website. I see it is also available on App Store. Is it possible that the future upgrades to software can be shown within the App Store, although I downloaded and installed it directly from elsewhere?

This will prevent me uninstalling the setup completely and downloading and installing a new one from the App Store.
No, unfortunately this is not possible.

You can only update software within the App Store that was download directly from the App Store.