Mac keyboard shortcuts
No need to try all key combos until it works, because you'll be disappointed. Check out this page from Apple Support, and you'll find, sadly, there is no reverse key combo because Finder has nothing to work with - no focus for the command.

Once the window is closed, not even Command - Tab > [minimized app icon] will open the app window!

The only way to open the app is to click on its icon in the Dock.